Add pub.dev target support

[marandaneto]

that would make it possible to automate https://github.com/getsentry/sentry-dart with Craft

The dart tooling already has pub.dev support https://dart.dev/tools/pub/publishing#publishing-your-package
we could use its own CLI.

something that we probably need to go around is the changelog structure, Craft requires a different structure than pub.dev https://dart.dev/tools/pub/package-layout#changelogmd

[marandaneto]

also https://github.com/getsentry/sentry-dart-plugin