build(deps): bump gatsby-plugin-sitemap from 5.9.0 to 5.11.1 in /docs

Bumps [gatsby-plugin-sitemap](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-sitemap) from 5.9.0 to 5.11.1.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-sitemap/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-sitemap)

---
updated-dependencies:
- dependency-name: gatsby-plugin-sitemap
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

docs/package-lock.json

@@ -24,8 +24,8 @@
     "gatsby-plugin-react-helmet": "^5.11.0",
     "gatsby-plugin-react-svg": "^3.1.0",
     "gatsby-plugin-robots-txt": "^1.7.0",
-    "gatsby-plugin-sharp": "^4.9.0",
-    "gatsby-plugin-sitemap": "^5.9.0",
+    "gatsby-plugin-sharp": "^4.11.1",
+    "gatsby-plugin-sitemap": "^5.11.1",
     "gatsby-remark-autolink-headers": "^5.11.1",
     "gatsby-remark-copy-linked-files": "^5.11.0",
     "gatsby-remark-external-links": "^0.0.4",
@@ -37,7 +37,7 @@
     "gatsby-transformer-sharp": "^4.11.0",
     "gatsby-transformer-yaml": "^4.11.0",
     "polished": "^4.1.4",
-    "postcss": "^8.4.6",
+    "postcss": "^8.4.12",
     "prism-react-renderer": "^1.3.1",
     "prop-types": "^15.8.1",
     "puppeteer": "^13.1.3",