Publish on app stores

[casimir]

The big ones:

• [x] Apple App Store (mobile)
• [x] Google Play Store

The would nice ones:

• [x] F-Droid → #170
• [x] IzzyOnDroid
• [ ] Apple App Store (desktop)
• [ ] Flathub → https://github.com/flathub/flathub/pull/5247
• [ ] AppImageHub(?)