Complete F-Droid submission, update download link

[holmesworcester]

F-Droid is the leading way to get apps for people who remove Google dependencies from their phones. Lots of our potential early adopters do this and expect this.

Check to make sure our submission was accepted, and then update the F-Droid download link on our homepage and change the opacity on the download button/badge back to normal.

https://gitlab.com/fdroid/rfp/-/issues/2289

They will do their own builds, so we might run into problems. More on what to expect here: https://f-droid.org/docs/Inclusion_How-To/

For example, we will probably need to use release tags for mobile.

[holmesworcester]

Possibly blocked by #1141

[holmesworcester]

Update: someone from the F-Droid team responded ~2 weeks ago and I missed the response due to Gitlab pointing to an older email. (That's fixed now so I'll see it if they respond again.)

They asked about building instructions. If there is anything we can do to give additional support to F-Droid folks getting Android builds set up, we should do that now.

The context here is that F-Droid builds all apps from source, to ensure they don't contain non-free software and for security reasons. So we have to help them do that as best we can.

[siepra]

This is blocked until we update NodeJS to 18 on mobile

[holmesworcester]

See: #2007