build: automate release packaging and version bumps with changesets

[zimeg]

Summary

This PR adds Changesets to this project for improved package release and publishing workflows:

$ npm run changeset

The above command might be run alongside enhancements and fixes to write entries for our next release. Some other packages use this for detailed release notes as kind example:

• @astrojs/rss: https://github.com/withastro/astro/blob/main/packages/astro-rss/CHANGELOG.md
• @biomejs/biome: https://github.com/biomejs/biome/blob/main/packages/%40biomejs/biome/CHANGELOG.md
• @slack/web-api: https://github.com/slackapi/node-slack-sdk/blob/main/packages/web-api/CHANGELOG.md

Preview

📚 https://github.com/slackapi/bolt-js/blob/changesets/.github/maintainers_guide.md#-updating-changesets

Notes

• We might consider adding the amazing @changeset-bot to this project for reminders in PR since not all changes require new entries so blocking CI would be rude. But perhaps that's a lot of noise?
• OIDC configurations are now available and required in place of access tokens. This can be setup if this all looks good:
  https://github.blog/changelog/2025-07-31-npm-trusted-publishing-with-oidc-is-generally-available/
• The publish GitHub Actions environment will also need to be setup with correct review permissions.

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 93.59%. Comparing base (a18c359) to head (0441ff2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2851   +/-   ##
=======================================
  Coverage   93.59%   93.59%           
=======================================
  Files          44       44           
  Lines        7855     7855           
  Branches      687      687           
=======================================
  Hits         7352     7352           
  Misses        498      498           
  Partials        5        5           

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[WilliamBergamin]

Nice work 🥇 looking forward to trying this out 🚀

[zimeg]

@WilliamBergamin Likewise I think this'll be meaningful for upcoming releases. Let's merge this and perhaps test in follow ups of #2827!

I'll configure the changesets bot, OIDC publishing, and the workflow configuration next.

[zimeg]

@WilliamBergamin Landing one more change that splits the workflow between changelogs and publish to match the latest node SDK changes. I forgot this might've blocked workflow permissions! 🚢