small grammar change

<!--
  Have any questions? Check out the contributing docs at https://gatsby.app/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

<!-- Write a brief description of the changes introduced by this PR -->

## Related Issues

<!--
  Link to the issue that is fixed by this PR (if there is one)
  e.g. Fixes #1234, Addresses #1234, Related to #1234, etc.
-->

<!--
  Have any questions? Check out the contributing docs at https://gatsby.dev/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

- Add small refactoring to the benchmarks apps.
- Fix benchmark query app warning:
```
warning Action createPage was called outside of its expected asynchronous lifecycle createPages in default-site-plugin.
```

## Related Issues

<!--
  Have any questions? Check out the contributing docs at https://gatsby.dev/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

Link for `createNodeField` was empty and clicking it just moved the page up. I think the link should point to https://www.gatsbyjs.org/docs/actions/#createNodeField

## Related Issues

<!--
  Link to the issue that is fixed by this PR (if there is one)
  e.g. Fixes #1234, Addresses #1234, Related to #1234, etc.
-->

This tiny change allows the gatsby-remark-embed-snippet plugin to correctly highlight ruby files.

The plugin allows embedding files like:

`embed:myfile.myext`

For many languages, the language name and the extension are the same e.g. .html or .js or .css.

However, for some languages, the extension does not match E.g. for ruby, the extension is `.rb` and the language is `ruby`. In the case where these do not map, the plugin relies on an internal map.

This adds the mapping from .rb to ruby, so that ruby files are highlighted correctly.

## Summary

- Affects only gatsby-remark-embed-snippet plugin
- Added a mapping from rb -> ruby files
- This means files called something.rb will be correctly highlighted as ruby

 - gatsby-remark-embed-snippet@3.2.4

…tyle (#12200)

Addressing issue [12199](#12199) where the default values couldn't be overwritten.

Co-authored-by: Ward Peeters <ward@coding-tech.com>

* test(gatsby-plugin-sitemap): Added tests

* feat(gatsby-plugin-sitemap): enable to create sitemap index too.

* docs(gatsby-plugin-sitemap): Update README

* Apply suggestions from code review

Co-Authored-By: tomoyukikashiro <ksrtmyk@gmail.com>

* fix(gatsby-plugin-sitemap): return statement ASAP.

* fix(gatsby-plugin-sitemap): use mock


Co-authored-by: Ward Peeters <ward@coding-tech.com>

This PR contains the following updates:

| Package | Type | Update | Change | References |
|---|---|---|---|---|
| gatsby | dependencies | patch | [`^2.1.29` -> `^2.1.30`](https://diff.intrinsic.com/gatsby/2.1.29/2.1.30) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-image | dependencies | patch | [`^2.0.31` -> `^2.0.32`](https://diff.intrinsic.com/gatsby-image/2.0.31/2.0.32) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-feed | dependencies | patch | [`^2.0.14` -> `^2.0.15`](https://diff.intrinsic.com/gatsby-plugin-feed/2.0.14/2.0.15) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-google-analytics | dependencies | patch | [`^2.0.16` -> `^2.0.17`](https://diff.intrinsic.com/gatsby-plugin-google-analytics/2.0.16/2.0.17) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-manifest | dependencies | patch | [`^2.0.22` -> `^2.0.23`](https://diff.intrinsic.com/gatsby-plugin-manifest/2.0.22/2.0.23) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-offline | dependencies | patch | [`^2.0.24` -> `^2.0.25`](https://diff.intrinsic.com/gatsby-plugin-offline/2.0.24/2.0.25) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-react-helmet | dependencies | patch | [`^3.0.8` -> `^3.0.9`](https://diff.intrinsic.com/gatsby-plugin-react-helmet/3.0.8/3.0.9) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-sharp | dependencies | patch | [`^2.0.26` -> `^2.0.27`](https://diff.intrinsic.com/gatsby-plugin-sharp/2.0.26/2.0.27) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-plugin-typography | dependencies | patch | [`^2.2.8` -> `^2.2.9`](https://diff.intrinsic.com/gatsby-plugin-typography/2.2.8/2.2.9) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-remark-copy-linked-files | dependencies | patch | [`^2.0.9` -> `^2.0.10`](https://diff.intrinsic.com/gatsby-remark-copy-linked-files/2.0.9/2.0.10) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-remark-prismjs | dependencies | patch | [`^3.2.4` -> `^3.2.5`](https://diff.intrinsic.com/gatsby-remark-prismjs/3.2.4/3.2.5) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-remark-responsive-iframe | dependencies | patch | [`^2.0.9` -> `^2.0.10`](https://diff.intrinsic.com/gatsby-remark-responsive-iframe/2.0.9/2.0.10) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-remark-smartypants | dependencies | patch | [`^2.0.8` -> `^2.0.9`](https://diff.intrinsic.com/gatsby-remark-smartypants/2.0.8/2.0.9) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-source-filesystem | dependencies | patch | [`^2.0.23` -> `^2.0.24`](https://diff.intrinsic.com/gatsby-source-filesystem/2.0.23/2.0.24) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-transformer-remark | dependencies | patch | [`^2.3.1` -> `^2.3.2`](https://diff.intrinsic.com/gatsby-transformer-remark/2.3.1/2.3.2) | [source](https://togithub.com/gatsbyjs/gatsby) |
| gatsby-transformer-sharp | dependencies | patch | [`^2.1.15` -> `^2.1.16`](https://diff.intrinsic.com/gatsby-transformer-sharp/2.1.15/2.1.16) | [source](https://togithub.com/gatsbyjs/gatsby) |

---

### Release Notes

<details>
<summary>gatsbyjs/gatsby</summary>

### [`v2.1.30`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.1.29...gatsby@2.1.30)

[Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.1.29...gatsby@2.1.30)

</details>

---

### Renovate configuration

:date: **Schedule**: At any time (no schedule defined).

:vertical_traffic_light: **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

:recycle: **Rebasing**: Whenever PR becomes conflicted, or if you modify the PR title to begin with "`rebase!`".

:ghost: **Immortal**: This PR will be recreated if closed unmerged. Get [config help](https://togithub.com/renovatebot/config-help/issues) if that's undesired.

---

 - [ ] <!-- renovate-rebase -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://togithub.com/marketplace/renovate). View repository job log [here](https://renovatebot.com/dashboard#gatsbyjs/gatsby).

## Description
 Running `yarn run develop` for gatsbyjs.org (`www/`) fails with the following errors on a fresh ubuntu 18.04 setup:

```
error Failed to process image /path/to/gatsby/www/.cache/gatsby-source-filesystem/31986f7e77b390d77efe1d58936176a0/db0d7d37f2039e29db5e4611a2a19392.png
  Error: vipspng: libpng read error
  vipspng: libpng read error
  vips2png: unable to write to buffer
```
Installing `libvips-dev` fixed the issue. 

This PR addresses the issue of informing users of the solution to a possible error on Linux

## Related Issues
 Fixes #12101

Picking up where #12264 left off:

- `presets.scale` _almost_ everywhere
- less `boxShadow: none` and `:hover { background: "none" }` overrides for links — we don’t need to overwrite this style anymore
- add `presets.letterSpacings` and use them
- add `colors.white` and use it
- import `radii` directly instead of doing `presets.radii[x]`
- rename `presets.animation` to `presets.transition`
- import `transition` directly instead of doing `presets.transition[x]`
- add `presets.shadows.cardActive`
- more `presets.space` refactoring
- remove Futura PT `specimen_files`, demo HTML, and „How to use web fonts“
- first improvements to the „Starters“ search input styles
- simplify things here and there 😉

 - gatsby-plugin-sitemap@2.0.8
 - gatsby-remark-images@3.0.9

…querying. (#12508)

 - gatsby-source-drupal@3.0.28

…irefox (#12449)

## Description

Collapsible component (the checkboxes in https://www.gatsbyjs.org/showcase/) isn’t scrolling properly in Firefox.

## Related Issues
#11574 
#11644

* change cacheId generation only when the icon file is available

* fix linter
yarn lint:js --fix

* update peerDependencies

* change to createContentDigest

* use fs-extra for consistency

* feat: add cache busting

used internal digest generator till the global one is available
converted the node api to use ASYNC await to simplify new code
added cache busting to favicon, manifest, and legacy head links

* test: add tests for cache busting

* Docs: added docs for cache busting to gatsby-plugin-manifest

* test: fix createContentDigest test failing

* fix: generateIcons not called when cache busting disabled

* test: add tests to confirm icons are being generated, or not as they're suppose to be.

* fix peer dep

* cleanup code

* clenaup tests

* fix windows test

<!--
  Have any questions? Check out the contributing docs at https://gatsby.app/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

This is the PR for issue #11277. It fixes the sanitizeName error.

<!-- Write a brief description of the changes introduced by this PR -->

## Related Issues

Related to #11277
<!--
  Link to the issue that is fixed by this PR (if there is one)
  e.g. Fixes #1234, Addresses #1234, Related to #1234, etc.
-->


Co-authored-by: Dustin Schau <DSchau@users.noreply.github.com>
Co-authored-by: Ward Peeters <ward@coding-tech.com>

* feat(gatsby-plugin-sharp): Configurable base64 width

Allows for using larger(or smaller) than the default `20px` width, trading size for quality via more/less pixels.

Adds the `base64Width` arg to the fixed & fluid nodes.

* chore(gatsby-plugin-sharp): Remove magic numbers

Provides added clarity for where these numbers are used.

Especially for the value of `72` where it's not clear if the value was for image or display density. `defaultBase64Width` improves clarity and keeps it DRY across both usages.

* fix(gatsby-image): Support placeholder image with backgroundColor

Place the `backgroundColor` div before/behind the placeholder img.

* chore(gatsby-image): Share common transitionDelay variable

They seem all intended to use the same duration of `0.25s`, `fluid` backgroundColor div actually used `0.35s` for some reason which seemed a possible typo, this corrects that and avoids it in future.

* feat(gatsby-plugin-sharp): Allow base64 format to differ, allow WEBP

For example, WEBP base64 placeholders with a `backgroundColor` as fallback while using JPG/PNG with WEBP for the `<picture>` element.

Adds the `forceBase64Format` config option.
Adds support for WEBP base64 images.

* chore(gatsby-image): Update test snapshot

* feat(gatsby-plugin-sharp): Support base64Width as a config option

Allows setting a project wide default, rather than having to request it per image.

Updates `defaultBase64Width` to be a function as `pluginOptions` has not initialized when assigned.

* feat(gatsby-plugin-sharp): Support forceBase64Format as query arg

* Change `density_72PPI` to `defaultImagePPI`

Co-Authored-By: polarathene <polarathene@users.noreply.github.com>

* Change `density_72PPI` to `defaultImagePPI` 2

Co-Authored-By: polarathene <polarathene@users.noreply.github.com>

<!--
  Have any questions? Check out the contributing docs at https://gatsby.dev/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

enable clickable link in documentation

## Related Issues

<!--
  Link to the issue that is fixed by this PR (if there is one)
  e.g. Fixes #1234, Addresses #1234, Related to #1234, etc.
-->

Built with GatsbyJS, hosted on netlify and with contentful as an CMS.

<!--
  Have any questions? Check out the contributing docs at https://gatsby.dev/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

<!-- Write a brief description of the changes introduced by this PR -->

## Related Issues

<!--
  Link to the issue that is fixed by this PR (if there is one)
  e.g. Fixes #1234, Addresses #1234, Related to #1234, etc.
-->

This adds an "Introduction" item to the sidebar of https://www.gatsbyjs.org/contributing/, similar to what we do for https://www.gatsbyjs.org/tutorial/ and https://www.gatsbyjs.org/docs/.

Currently, the only way to bring up the "Contributing" "landing page" is by clicking "Contributing" in the main navigationg in the header, which might be a bit confusing.

From a Slack conversation with @marcysutton. 👋

 - gatsby-image@2.0.33
 - gatsby-plugin-manifest@2.0.24
 - gatsby-plugin-sharp@2.0.28
 - gatsby-plugin-sitemap@2.0.9
 - gatsby-source-contentful@2.0.38
 - gatsby-source-mongodb@2.0.14
 - gatsby-transformer-sharp@2.1.17
 - gatsby-transformer-sqip@2.0.24