Bump versionCode to 13 and versionName to 3.0.0. The Flutter app ended at
2.0.0-alpha.3+12 (versionCode 12), so 13 keeps the eventual com.subtracks
release an in-place upgrade.
Metadata was still inherited from the Flutter app:
- add the changelog for versionCode 13
- rewrite the descriptions for the native app
- replace the Flutter phone screenshots with native renders, and mute the
screenshot fixture palette so the placeholder artwork reads as covers
austinried