Add information regarding mapping of analog triggers on Android

[WIrral]

The HID events for android are different then the ones on other systems.

Most of them seem to be compatible, though analog triggers do not work with the standard right or left trigger. After some trial and error I figured that using the simulation controls Brake (for left trigger) and Accelerator (for right trigger) works great.

I added these findings to the readme under notes, with a reference to it in features by the android compatibility