Add Adafruit TFT Experiment (rev A)
There will be a revision but get the basics in for now.
This successfully displays on a TL040HDS20-B1502A screen with:
```
import board
from framebufferio import FramebufferDisplay
from dotclockframebuffer import DotClockFramebuffer
from displayio import release_displays
tft_pins = board.TFT
tft_timings = {
"frequency": 6_500_000,
"width": 720,
"height": 720,
"hsync_pulse_width": 20,
"hsync_front_porch": 40,
"hsync_back_porch": 40,
"vsync_pulse_width": 10,
"vsync_front_porch": 40,
"vsync_back_porch": 40,
"hsync_idle_low": False,
"vsync_idle_low": False,
"de_idle_high": False,
"pclk_active_high": False,
"pclk_idle_high": False,
}
release_displays()
fb = DotClockFramebuffer(**tft_pins, **tft_timings)
disp = FramebufferDisplay(fb)
```
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