[Monorepo] PR "move" and wrapping up

[pkra]

To wrap up the monorepo move, please complete the following:

• [ ] review PRs (see link list below)
  • [ ] close PRs that were "moved" correctly
  • [ ] handle PRs from forks (which could not be "moved" the same way)
  • either alert authors to make new PRs to on the ARIA repository and close the PR
  • or (to maintain a useful diff) create a branch (e.g., "old_main") and change those PRs to target that branch
• [ ] merge "closing" PR #548

PR list

• [ ] #396 => TODO (pkra: this one was too messy to move over due to the aam table changes)
• [x] #538 => https://github.com/w3c/aria/pull/2339
• [x] #359 => https://github.com/w3c/aria/pull/2224
• [x] #401 => https://github.com/w3c/aria/pull/2222
• [x] #451 => https://github.com/w3c/aria/pull/2221
• [x] #484 => https://github.com/w3c/aria/pull/2218
• [x] #510 => https://github.com/w3c/aria/pull/2217
• [x] #529 => https://github.com/w3c/aria/pull/2215
• [x] #522 => TODO (from fork)
• [x] #521 => TODO (from fork)
• [x] #516 => https://github.com/w3c/aria/pull/2216
• [x] #540 => https://github.com/w3c/aria/pull/2212
• [x] #539 => https://github.com/w3c/aria/pull/2213
• [x] #533 => https://github.com/w3c/aria/pull/2214
• [x] #454 => https://github.com/w3c/aria/pull/2220
• [x] #481 => https://github.com/w3c/aria/pull/2219
• [x] #395 => https://github.com/w3c/aria/pull/2223