Include documentation for Raspberry PI

The following information can be included in the documentation, regarding Raspberry PI.

The library was successfully tested on a Raspberry PI 3, running Processing 4.0b7
Before using the library, you can check if the RPI has detected the MIDI controller, by running `amidi -l`

```bash
pi@raspberrypi:~/Documents/processing-4.0b7 $ amidi -l
Dir Device Name
IO hw:2,0,0 Launch Control MIDI 1
```

**If the command above does not show your MIDI controller, then the library will not detect it either.**

Once you confirmed that the RPI has detected the controller, you can use the value under Device between brackets, like so:
```Java
controller = new LaunchControl(this, true, "Control [hw:2,0,0]");
```