Provide TypeScript types for config files

**Is your feature request related to a problem? Please describe.**

I'm writing tooling around AllContributors in TypeScript and can't find any officially-sanctioned types anywhere. Do they exist?

**Describe the solution you'd like**

Either as part of an `all-contributors` package -maybe that one?- or as a separate typings package, perhaps?

**Describe alternatives you've considered**

I'm writing them myself but it would be lovely to have a formal source to pull from.

**Additional context**

Here's a TypeScript interface based on the current docs: https://github.com/JoshuaKGoldberg/all-contributors-inferred/blob/0fa4ed0f9a7dc05421295f238668f9285252e6cb/src/types.ts#L10

I'd be happy to contribute these if you want them. 🙂