Feature request: Fetch all repositories accessible by github app

[pettermk]

First of all, thanks for a great library! I am using it in my project and noticed I wasn't able to fetch the repo metadata my github app can access. This is the API doc, let me know if I've somehow missed the possibility to use it.

https://docs.github.com/en/rest/apps/installations#list-repositories-accessible-to-the-app-installation

I am forking off and working on a PR, creating this issue for tracking it.

BR, Petter