Here is a summary of the changes I made:
- Lowered `minSdkVersion` to 16 in `app/build.gradle`.
- Removed unsupported features from `AndroidManifest.xml` and layout files.
- Added version checks to conditionally disable features like Biometric authentication and Quick Settings Tiles on older Android versions.
- Ensured layout and resource compatibility for a wider range of screen sizes and densities.
- Removed a git dependency from the build script.
- Reverted `compileSdk` and `targetSdk` to 35.
- Conditionally disabled camera functionality on API < 21.
- Conditionally disabled the About screen on API < 21.
I set CompactDividerDecoration to transparant, because that was already
effectively the case. I think we can remove this class entirely, but
I'll do that in a separate PR.
This also fixes an issue with the use of the Iconics library where it was
initialized twice. I also removed the dependency to [AndroidX Preference
eXtended](https://github.com/takisoft/preferencex-android), as there don't seem
to be any issues with using the vanilla AndroidX preference library anymore.