[Feature Request] Add HID battery feedback

[LeeNX]

Adding an input HID descriptor that has the battery level populated. Means that applications that have access to the HID descriptor, can also read the battery level.

Not all applications have access to the GATT level of the device.

[LeeNX]

The original idea was to report on the input HID report, I see that SInput as access via the Feature Reports, which works.

My first tests with using the input HID report, was that most hosts don't know what to do with battery level and just make it look like an analog trigger, which can still work, but I think any game or application might try and hook it into an input.