file attinyx16.py analog pins only for output? (the text of the definitions tells us)

I am using an Adafruit Gamepad QT (ID 5743).
While diving into this Adafruit_Circuitpython_seesaw module I found that the text in the file attinyx16.py,
lines 21-22 read:
```
"""The pins capable of analog output"""
analog_pins = (0, 1, 2, 3, 4, 5, 14, 15, 16)

```

however, this file is also used for the Adafruit Gamepad QT (ID 5743).

The text in Adafruit Learn for the Gamepad QT
[pinouts](https://learn.adafruit.com/gamepad-qt/pinouts)
says the following:

```
Joystick
This is the 2-axis joystick located on the left side of the board.

X-axis - The joystick x-axis (horizontal) is on pin 14 in the seesaw firmware.
Y-axis - The joystick y-axis (vertical) is on pin 15 in the seesaw firmware.
```

In test scripts these Joystick X-Y values are usually read using commands like this:
```
x = 1023 - seesaw.analog_read(14)
y = 1023 - seesaw.analog_read(15)
```

I suggest to change the text in file attynx16.py, lines 21-22, and have them read (for example) like:
```
"""The pins capable of analog input and output"""
analog_pins = (0, 1, 2, 3, 4, 5, 14, 15, 16)

```

Open attinyx16.py and inspect lines 21-22 alongside the Gamepad QT pinout and the issue's analog_read(14) and analog_read(15) examples. Update the analog pin description to cover input and output, then verify that the listed pins and wording match the documented joystick usage.

Written by the indexing model from the issue text.