Migrate to pnpm and changesets

[jakebailey]

This switches the repo to pnpm/changesets, the monorepo and deployment method we use for dt-tools and attw (and me personally).

Notably:

• Internal deps are now marked as workspace:*, so we don't need to do the bumping manually.
• Publishing is now via pnpm publish -r, which rewrites the specifiers automatically.
• Changesets auto-bumps the version numbers themselves.
• Builds are a lot faster (multiple minutes better).

TODO:

• Figure out the changesets private package setting; see also Configure changesets to ignore private packages DefinitelyTyped-tools#1003
• Perhaps it should be workspace:^ to be less strict.
  • For now, no, as we used explicit deps previously.
• Docs on how to use changesets
• Make CI expectations happy

[jakebailey]

Hey, it works.

[jakebailey]

Yay, got it working on all OSs.

[andrewbranch]

Amazing. What’s the remaining CI status thing?

[jakebailey]

Amazing. What’s the remaining CI status thing?

GitHub is configured to require the CI check named "tests" but that doesn't work when it turns into a matrix as the name changed. Which is silly. I plan to use this trick: https://github.com/microsoft/typescript-benchmarking/blob/7371a75e3d5862eaffabaca749b94cfa9b934bc9/.github/workflows/ci.yml#L132

[jakebailey]

This is looking good to go, but I'm going to do one last check and pack each package and compare it to what's on npm to ensure that the build is actually working as intended.

[jakebailey]

Diffing was fruitful and found a few issues. The packages that can be published after this PR should be correct, plus or minus that the other gatsby 5 and such PR updated some deps.

[github-actions]

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