chore(ci): add pkg.pr.new for continuous release

[kricsleo]

resolves #484

⚠️ This requires install the pkg-pr-new GitHub Application first:

First install the GitHub Application.

Important

Make sure it's installed on the repository before trying to publish a package. To read about the permissions the app needs, check stackblitz-labs/pkg.pr.new#305.

[pi0]

Appreciate the PR. Please check unjs/changelogen#215 for some context. Once solved, our standard release tool (changelogen) will enable it for unjs repos.