chore: add v4 release notes

Author: ascorbic

README.md

@@ -14,6 +14,9 @@
   </a>
 </p>
 
+## What's new in this version
+
+Version 4 is a complete rewrite of the Essential Next.js plugin. For full details of everything that's new, see [the v4 release notes](https://github.com/netlify/netlify-plugin-nextjs/blob/main/docs/release-notes/v4.md)
 
 ## Installing the beta
 

docs/large-functions.md

@@ -10,7 +10,9 @@ There are two possible causes for this, each with its own solution. The list of
     [functions]
     excluded_files = "node_modules/electron/**/*"
     ```
-    If you do need large modules (e.g. if you are running Puppeteer in a Next API route), consider changing to a Netlify function.
+    If you do need large modules (e.g. if you are running Puppeteer in a Next API route), consider changing to a Netlify function which will have less overhead than the equivalent Next.js function.
 
 - **Large numbers of pre-rendered pages**
-If you have a very large number of pre-rendered pages, these can take up a lot of space in the function. There are two approaches to fixing this. One is to consider deferring the building of the pages. If you set `fallback = "blocking"`, the rendering will be deferred until the first user requests the page. This is a good choice for low-traffic pages. It reduces build and deploy time, and can make your bundle a lot smaller. The other option is to enable an experimental feature that moves static files out of the function bundle. To do this, set the environment variable `EXPERIMENTAL_MOVE_STATIC_PAGES` to true.
+  If you have a very large number of pre-rendered pages, these can take up a lot of space in the function. There are two approaches to fixing this. One is to consider deferring the building of the pages. If you return `fallback: "blocking"` from `getStaticPaths` the rendering will be deferred until the first user requests the page. This is a good choice for low-traffic pages. It reduces build and deploy time, and can make your bundle a lot smaller. 
+  
+  The other option is to enable an experimental feature that moves static files out of the function bundle. To do this, set the environment variable `EXPERIMENTAL_MOVE_STATIC_PAGES` to true.

docs/release-notes/v4.md

@@ -0,0 +1,30 @@
+# Essential Next.js plugin v4 release notes
+
+This is a full rewrite of the Essential Next.js plugin, with a new architecture that gives greater compatibility and stability.
+
+## What's new
+
+- Full support for Next.js rewrites, redirects and headers.
+- Removes requirement for the `target` to be set to `serverless`, which is deprecated in Next 12.
+- Faster builds and deploys. Instead of generating one function per route, there are just three functions per site and a much smaller list of rewrites.
+- Bundling now uses Next.js's own node-file-trace, giving more predictable results and smaller uploads.
+- Full support for Netlify's new [persistent On-Demand Builders](https://ntl.fyi/odb). Return `fallback: "blocking"` from `getStaticPaths` and your rendering will be deferred until the first page load, then persisted globally.
+- A new image server, built on Nuxt's [ipx](https://github.com/unjs/ipx/). This is a high-performance, framework-agnostic image server based on sharp. This implementation uses On-Demand Builders to persist transformed images globally. Improved source image caching reduces time-to-first-byte for new transforms.
+- Simplified configuration. You no longer need to set any Netlify-specific configuration options. For example, in a monorepo all you need to do is set `publish` to point to your `.next` directory and you can build the site in any way you like.
+
+## Installing the beta
+
+If you would like to try the beta, you should install it manually like this:
+
+- Install the module:
+```shell
+npm install -D @netlify/plugin-nextjs@beta
+```
+- Change the `publish` directory to `.next`  and add the plugin to `netlify.toml` if not already installed:
+```toml
+[build]
+publish = ".next"
+
+[[plugins]]
+package = "@netlify/plugin-nextjs"
+```