Integrate (semi-)automatic changelog generation for GitHub Releases

[rdw-software]

Goals:

• [x] Change logs can be generated from git commits automatically
• [x] They are appended to GitHub Releaes automatically (example here)

Roadmap:

• [x] Implement changelog generation via C_BuildTools (for now)
  • [x] API to discover the SECOND latest git version (git tag --sort=-creatordate | head -2 | tail -1)
  • [x] API to discover all PRs between two releases (git log v3.0.0...v2.18.0 --merges --pretty="format:* \[[`%h`](https://github.com/evo-lua/evo-luvi/commit/%H)] - %b"
  • [x] API to create a Markdown rendition of a given changelog description
  • [x] API to insert the PRs, contributors, and human-readable notes (optional)
  • [x] API to create a log for the latest tag and save it to CHANGELOG.MD
  • [x] For human-readable summaries, need to store a Lua table/JSON DB somewhere (and update manually)
• [x] Add scripts to generate a CHANGELOG.MD for the current (latest) release tag
• [x] Ignore this file via .gitignore (no need to commit it as it's ephemeral)
• [x] Add an extra step to the release workflows that generates a changelog for the last two versions (vOLD..vNEW)
• [x] Update all CI release workflows to automatically set this file's contents as the release body (it's idempotent)

Formats (TBD):

• git commits only (see luvit releases)
• https://github.com/nodejs/node/blob/1bbd14eac20684a733250629c7896262c0ca4576/doc/changelogs/CHANGELOG_V19.md
• Manually-added notes (see existing changelogger tool)

[rdw-software]

Examples of some more user-friendly changelogs: VS Code, BNET, GitHub Desktop.

Unfortunately those don't look like they could be autogenerated.

[rdw-software]

Initial working version done, but needs cleanup/refactoring and testing with some actual PRs being available. I'll review this once some other changes have been merged, but here's a temporary release (will be deleted later) that demonstrates that it works: