[@changesets/changelog-github] Contributor-only thanks option (skip thanks for repo maintainers) #2149

The problem

@changesets/changelog-github currently renders every release line as

- [#210](…) [`4f75d34`](…) Thanks [@author](https://github.com/author)! - <summary>

For solo-maintained (or small-team) projects, that means every "Version
Packages" PR reads "Thanks @maintainer! - …" on every entry, i.e. the
maintainer is publicly thanking themselves. 🙃 The existing disableThanks
option is a blunt switch: it hides thanks for everyone, which then
also silences the acknowledgement that outside contributors are
supposed to get.

Proposed option

An allow/deny list, or a maintainers list, that suppresses the "Thanks
@user!" chunk only when the resolved author matches one of the
configured GitHub logins. Everyone else keeps their thanks. Rough shape:

"changelog": [
  "@changesets/changelog-github",
  {
    "repo": "org/name",
    "maintainers": ["castastrophe"]
  }
]

Semantics:

• When users (the joined "@A, @b" list built at
  changesets-changelog-github.esm.js:144) contains only logins from
  maintainers, drop the entire Thanks …! clause.
• When users mixes a maintainer with outside contributors, keep the
  full list — that credit is still meaningful.
• If users is empty (no linked commit/PR author), behavior is
  unchanged.

Backwards compatible: default maintainers to [] and the current output is untouched.

Alternative considered

Wrapping the package with a local changelog module that post-processes
getReleaseLine's output and strips the maintainer's thanks with a
regex. It works (see
example wrapper),
but it duplicates the option surface, adds a resolve step to
.changeset/config.json, and every consumer that wants the same
behavior has to write the same tiny wrapper. A first-class option
would let projects express "the maintainer is us; only shout out real contributors" without a bespoke shim.

Willing to help

Happy to open a PR wiring this into
packages/changelog-github/src/index.ts and the option validation in
@changesets/config if the shape above is acceptable.