ci: switch to changesets for releases

[alexander-akait]

Adopts the same release flow as webpack/sass-loader: a custom changelog
generator under .changeset/, a release workflow that opens a release
PR or publishes on merge to main, and version/release npm scripts
backed by @changesets/cli. Drops standard-version in favor of this
setup.

[linux-foundation-easycla]

• ❌ - login: @claude / name: Claude. The commit (1e496a9) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.21%. Comparing base (61dcff1) to head (1e496a9).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #591   +/-   ##
=======================================
  Coverage   92.21%   92.21%           
=======================================
  Files           3        3           
  Lines         167      167           
  Branches       44       44           
=======================================
  Hits          154      154           
  Misses         12       12           
  Partials        1        1           

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