docs - add manual redirects scripts

[lukegalbraithrussell]

Summary

Docusaurus has a redirects plugin. It doesn't handle redirecting from hashes (like concepts#web-api) which is how the old site worked. I wrote a script to redirect the pages like concepst#web-api to concepts/web-api.

I also used the redirects plugin for normal, specific, redirects.

It seems the two are clashing. With the plugin, and only in prod, /concepts#web-api gets redirect to /concepts/#web-api instead, which doesn't work. Changing trailingSlashes param doesn't fix it. Removing the plugin fixes it, though, so I added an additional redirects script for redirecting specific pages: redirects-pages.js.

The only pages redirected right now are category pages that didn't have content, but are links people might have bookmarked. And /, as there's no landing page yet. All just go to getting-started

I tested it on build and serve, but also the previous iteration worked there. So I also tested the setup on a deployed docusaurus site on a personal repo. It works in prod there.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.07%. Comparing base (9b444ae) to head (7160477).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2178   +/-   ##
=======================================
  Coverage   82.07%   82.07%           
=======================================
  Files          18       18           
  Lines        1545     1545           
  Branches      443      443           
=======================================
  Hits         1268     1268           
  Misses        179      179           
  Partials       98       98           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[zimeg]

LGTM! Testing this in production might be the most sure way to confirm these changes 🚀 😬 These redirects seem fine too but I'd hesitate a bit before adding much more logic around this!

[zimeg]

Nit: I think the inner contents of this function can be indented. But this could be ignored. Surprised the linter isn't catching this!