🛠 Tooling: Move release-it.d.ts to release-it or DefinitelyTyped

[JoshuaKGoldberg]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

https://github.com/webpro/release-it is written in JavaScript and doesn't ship its own .d.ts types. The general TypeScript community consensus for packages like that is to write the types in https://github.com/DefinitelyTyped/DefinitelyTyped. That'd be better than having a src/release-it.d.ts checked into this repo.

Once there are TypeScript types available for the release-it package, we can use them here. Accepting PRs!

Additional Info

cc @webpro as an FYI.