build: automate release packaging and version bumps with changesets

[zimeg]

Summary

This PR adds Changesets to these packages for improved package release and publishing workflows:

$ npm run changeset

The above command might be run alongside changes in packages to write entries for that package's next release. 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

We might consider adding this to our release workflows to automate version bumps between dependent packages - as example @slack/web-api imports @slack/types - in addition to the other release and publishing scripts.

Preview

📚 https://github.com/slackapi/node-slack-sdk/blob/zimeg-build-changesets/.github/maintainers_guide.md#-updating-changesets

👾 Publish Workflow: We might experiment with the changes of #2474 to confirm that this publishes packages and creates releases as expected!

Notes

• A few strategies of bumping dependent packages are available. The default is used now and it doesn't bump the minimum required version unless a recent change requires a newer version.
• The tags for upcoming milestones are suggested to be changed to @slack/package@next instead of a set version.
• Instructions toward pre-releases with Changesets are noted as being complicated and were left for future changes: https://akinoccc.github.io/changesets/guide/advance/pre-releases
• 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 93.09%. Comparing base (45452bc) to head (4c4959a).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2483   +/-   ##
=======================================
  Coverage   93.09%   93.09%           
=======================================
  Files          40       40           
  Lines       11239    11239           
  Branches      713      713           
=======================================
  Hits        10463    10463           
  Misses        764      764           
  Partials       12       12           

Flag	Coverage Δ
cli-hooks	95.23% <ø> (ø)
cli-test	94.79% <ø> (ø)
oauth	77.39% <ø> (ø)
socket-mode	61.87% <ø> (ø)
web-api	98.11% <ø> (ø)
webhook	96.66% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[zimeg]

Noting some additional nuance and thoughts in these changes for the wonderful reviewers 🌚

[zimeg]

📚 note: The CHANGELOG file specific to each package might match what's shown in GitHub releases but also perhaps we can use this downstream in documentation?

[zimeg]

👁️‍🗨️ note: These package are EOL and shouldn't be published so the private field is used.

[zimeg]

📺 note: We're using node@24 for a supported npm version:

Trusted publishing requires npm CLI version 11.5.1 or later.

🔗 https://docs.npmjs.com/trusted-publishers