Improve @next-bundle-analyzer Documentation

[slongdotexe]

Goals

1. Improve documentation for @next-bundle-analyzer, relating to the following points:

• Usage with new webpack-bundle-analyzer features, specifically filter by initial chunks (effectively filter by page):
  Allow filtering the list of entrypoints webpack-contrib/webpack-bundle-analyzer#624
  This could be quite useful for exploring page specific chunks.
• Manual configuration of Webpack Bundle Analyzer for advanced usage.
• Call out that older versions of @next-bundle-analyzer don't support several props.

2. Allow more options to be passed into @next-bundle-analyzer or otherwise better highlight advanced config options.
3. Provide backlinks to webpack-bundle-analyzer documentation, either for manual config or expanded config options for @next-bundle-analyzer
4. Provide info on how Next CLI calculates page sizes in the CLI output and any potential caveats to this. Potentially provide links for further reading.

Non-Goals

Background

I've recently been working to understand some performance-related matters that an application I maintain is experiencing. While the NextJS docs around this are a great start, I think that some improvements need to be made to improve context and visibility for this tooling. I believe this would benefit the community.

I was particularly stumped by an older version of the Next analyzer in our repo, which doesn't support as many options as the updated version. I've also noticed that some of the non-configurable configs are not quite compatible with the permissible options for the analyser.
https://github.com/vercel/next.js/blob/canary/packages/next-bundle-analyzer/index.js#L13

E.g, I found that providing json for analyzerMode will still result in a HTML file being saved. There's also a few options that are omitted altogether which is understandable but I think it would be great to have an example of manually including your own config for these slightly more advanced options.

Proposal

I'm interested in working on this feature.
I believe it is mostly a documentation task, with possibly some small modifications to the @next-bundle-analyzer package if we agree to allow some of the above-proposed changes.

I think adding to this existing page is likely the best place for some of this information:
https://nextjs.org/docs/app/building-your-application/optimizing/bundle-analyzer