Enable access to Friends via API

[AnOpenSauceDev]

Please confirm the following.

• I checked the existing issues for duplicate feature requests
• I have checked that this feature request is not on our roadmap

What parts of Modrinth is your feature request related too?

API, App

Is your suggested feature related to a problem? Please describe.

I noticed that the Modrinth App now has a Friends feature that requires a Modrinth account to use. Unfortunately, I haven't been able to test this feature to see what API calls it makes, and I don't know if the API used for the feature is subject to change, as there isn't anything about it on the docs.

Describe the solution you'd like

Having the ability to access a user's friends list through an official API, and to check if a friend is playing Minecraft under an instance. This would allow for mods to take advantage of the Friends feature, whether that be Essential-style world invites or indicating if a player is a friend in the user list.

Describe alternatives you've considered

Possibly using whatever undocumented API features that Friends uses. I dislike this alternative, as an undocumented API is likely to silently break and probably isn't supposed to be used outside of the Modrinth App.

Additional context

I worked on a social mod that used a friends system and possible Modrinth integration, but I never finished it due to having to the overhead of running my own servers + lack of confidence that it would have any users.

The friend system Modrinth provides fixes those problems, as I wouldn't have to have a database + server for handling the friends a user has, and their existing friends would already be provided via Modrinth.