refactor: extend android browser helper classes

[dargmuesli]

Instead of maintaining a copy of certain android-browser-helper classes, extend them.

Done in this project by modifying the base classes. Submitted a PR upstream, tracking here.

See:

• refactor: clarify overrides #44

Waiting for:

• Custom headers with TWALauncher GoogleChrome/android-browser-helper#329
• feat(twa-launcher): allow adding extra to twa intent GoogleChrome/android-browser-helper#562