Add Funkwhale's F-Droid repository

[taivlam]

Is your feature request related to a problem? Please describe.
I would like the custom Funkwhale repository to be on the list of Droid-ify's optional repositories.

Describe the solution you'd like
I would like the Funkwhale repository to be added on the list of Droid-ify's optional repositories.

Describe alternatives you've considered
I could manually add Funkwhale's repository app info into Droid-ify, but I can't seem to do this by scanning the QR code in Binary Eye and using the "Share with..." menu with the output of the QR code.

Additional context
From a recent Funkwhale blog post, Funkwhale's repo is described to offer current versions of its app sooner than the official F-Droid version.

From my understanding, this situation is similar to that of Newpipe: there is a version officially published by F-Droid, but it also maintains its own F-Droid repo so that versions closer to upstream can be given to users.

[HarriBuh]

You can easily add it to your current repos, why would you want it to become officially added? I don't see any advantages here.

[serrq]

Because lack of repo backup/restore feature...

[Iamlooker]

Merge with #349