Offer a way for local admins to interact with the appstore to leave reviews and comments from within their local instance

Currently possible to log into the apps.nextcloud.com site and leave reviews through Github. But about adding the ability for admins to leave reviews written from within their home Nextcloud after installing the app? I realize this relates to the server repo, but I think it is better to ask here in regards to the appstore conceptually.

Would pair very nicely with:
- #1266
- #947
- #890
- #593 to avoid admins spamming comments or reviews altogether.

And fewer admins would be frustrated if these nice-to-haves were part of their internal app installation process:
- #566
- #765
- #764

It would be a huge step forward for the application and review leaving process. It would also require some major refinements to the existing appstore before it would make sense. :heart:

_Total :pie:-in-the-:cloud: idea. Cheers._