registerSysBrightness static method
register or unregister system brightness.if register the system brightness observer, current window brightness wil changed by system brightness's change.
only for android
@param isRegister:true register system brightness :false unregister system brightnessImplementation
static Future<void> registerSysBrightness(bool isRegister) async {
await _nativeAPI.registerSysBrightness(BoolMsg()..value = isRegister);
}