Add touch test event

    - Copied from https://stackoverflow.com/a/54986161/ by Attila (https://stackoverflow.com/users/1327762/attila),

    - CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/)

    - This is also what powers the display code in `poolpay/display`, however, this is the original version of the script

- `test_touch.py`

    - Use `evdev` to get touch events, prints many of them (including coordinates)

#!/usr/bin/env python3

import evdev

touch = evdev.InputDevice('/dev/input/event0')

touch.grab()

coords = {}

for raw_event in touch.read_loop():

    if raw_event.type == evdev.ecodes.EV_ABS:

        coords[evdev.ecodes.ABS[raw_event.code]] = raw_event.value

    elif raw_event.type == evdev.ecodes.EV_SYN:

        print(coords["ABS_X"], coords["ABS_Y"], end="                \r")

    elif raw_event.type == evdev.ecodes.EV_KEY:

        print(evdev.ecodes.keys[raw_event.code], raw_event.value)