Possible solution for updating battery.

[chestwood96]

First of all thanks for making this.

I think I may have found a solution for updating the battery percentage.

Adding a call to this->hid->setBatteryLevel(level); in the setBatteryLevel of the BleKeyboard class makes the updating work for me.

However setting the battery level before "begin" causes an exception, so I am not sure if this is a viable solution. Maybe add a dedicated notify function or something?