ci: add napi release flow

Follow oxc's napi/parser layout: the crate's package.json is the
published `mdtidy`, and the per-platform packages are generated at
release time by `napi create-npm-dirs`, so nothing under packages/ is
kept in git. Platform packages use napi's unscoped default names,
because `@mdtidy` on npm belongs to someone else.

Add musl and Windows arm64 targets. Linux gnu builds with napi-cross
so the addon needs only glibc 2.17. The workflow runs by hand and
needs an NPM_TOKEN secret, since trusted publishing can't be set up
for packages that don't exist yet.