Bug Fixes
- KEYCODE_BACK appeared twice in the keycode list.
- crashed when the battery optimisation settings couldn't be found.
- some trigger keys have no name.
- unable to uncheck the "show volume dialog" flag.
- on some devices (e.g Oxygen OS 10),  the volume buttons up keyevents need to be consumed to stop them from changing the volume when performing an action.
- couldn't necessarily press the back button to get back to Key Mapper when opening the accessibility settings.

Added
- support for Jelly Bean 4.2 and 4.3.
- setting to show the toast message when an action fails to perform.
- action to open the device settings.
- action to open a URL.
- action to switch the input method (ROOT only)
- action to show the power dialog
- action to lock the device without root (only Android 9.0 Pie or newer)
- action to toggle split screen

Changes
- Removed Firebase.
