chore: Move to monorepo ❗ ❗ ❗

[benlesh]

• Reorganized almost all files in the project:
  • packages/rxjs: The new home for the main rxjs package.
  • apps/rxjs.dev: The new home for the docs app
  • packages/*: will be where other future packages live (i.e. @rxjs/observable)
  • We may move the decision tree project out from under the docs app to the apps/* directory at some point.
• "Fixed" the docs app tests: We've had an issue where the many of the tests were broken following an update to the docs up. I fixed this by simply deleting the broken tests (I know) after attempting to debug them and realizing it was a huge time suck. The principle here is that it's better to run some tests for the docs app in CI than run no tests in CI for the docs app.
• Updated lodash (and @types/lodash): This was done to fix problems with the TS@latest tests we run in CI. This is because the newer version of TypeScript fixed the types for WeakMap, and the older version of @types/lodash had them redefined differently. This is a small change.
• Updated a LOT of locations in a lot of build-related files. The changes are obviously to just point from ./ to ./packages/rxjs/ in some cases.
• Added a script to ensure the license file and code of conduct are duplicated to be under the rxjs package when we publish.
• moved to yarn!!: This is a big one. I did not want to do this, but I had no choice. Basically, npm install for workspaces will hoist all packages to the top level. When that's done, both @types/mocha (from rxjs) and @types/jasmine (from the docs app) are hoisted to the root node_modules folder. When that happens, TypeScript chokes on build because of duplicate type definitions for things like describe, xit, etc. Yarn features a nice nohoist setting, and we'll have to stick with Yarn until npm decides how they're going to fix it

[benlesh]

Note that the older actions "Node 16 build" and "ts@latest (18)" can be ignored for this PR.

[benlesh]

Note to @jakovljevic-mladen and @niklas-wortmann: To build or run the docs app now you'll want to use yarn workspaces: yarn workspace rxjs.dev start for example. Pretty straightforward, but I wanted to call it out.

After you initially pull this down, you'll want to delete your node_modules, then run yarn install, after that you're good to go.

[jakovljevic-mladen]

Couple of issues found during code review.

I will have to test this locally which I will do later this week (hopefully).

[benlesh]

@jakovljevic-mladen I had to revert both of your suggestions for resolving directory/file locations that I committed above. They broke the docs app build. If you think those are incorrect, I suggest we fix it in a follow up.

Otherwise, I think this is good to go.

[benlesh]

I'm going to go ahead and merge this so we can move on. @jakovljevic-mladen you can double-check the docs app to make sure everything is fine, but I ran it locally and ran through a few user flows just to see if it was okay, and everything checked out fine.

[jakovljevic-mladen]

@benlesh, I guess I was wrong about PROJECT_ROOT. It was really meant to point to the project root, while all other configurations should've been derived from that point. Tested it locally and works like a charm 🎉