Drop Support for Android 4.4

While the project generated by Bubblewrap supports Android 4.4 (Kitkat) and above, Chrome has moved to support Android 5.0 (Lollipop) and above.

Even though support for TWAs across browsers has increased, those devices are less likely to have a compatible one installed. Additionally, when the Custom Tabs / browser fallback are used user reviews are generally worse when the WebView fallback is used.

As a caveat, the Android WebView doesn't support all the features from the web platform, which means apps may not work as intended in this fallback.

There are two possible approaches to improve this:

1. Make the WebView fallback the default
2. Update Bubblewrap to generate projects targeting Android 5.0 (Lollipop) and above.