Add a flatpak nightly build

[Etaash-mathamsetty]

Problem description

I really don't want to keep downloading app images from the latest CI from the beta/main branch.
It would also help catch random bugs that were created as a result of certain PR's

Feature description

To fix this problem we could introduce a nightly build that one can download from flatpak

Alternatives

download the app image every day?

Additional information

No response

[Nocccer]

@flavioislima I was also thinking that the beta channel gets updated on each merge. So we have the stable and a up to date dev version. Does flatpak supports a experimental version? It would be really good to have this like proton experimental, but that would be another version. I think it is not possible but having a up to date beta version would be awesome.

[imLinguin]

If it wouldn't be possible on flathub, we can always spin up our own repo for highly unstable releases

[Nocccer]

flathub/flathub#2975
Flathub seems not to allow nightly.

[Etaash-mathamsetty]

flathub/flathub#2975 Flathub seems not to allow nightly.

I mean they said that it required "prior discussion", so all we have to do is ask them...
and by nightly I mean every day or every 2 days, which is not "every commit"