Modify the brightness property.

[geekguy-wy]

To make the library consistent with displayio, modify the brightness property so it uses a float instead of an int.

[caternuson]

With a range 0.0 to 1.0:
https://circuitpython.readthedocs.io/en/latest/shared-bindings/displayio/Display.html#displayio.Display.brightness

[geekguy-wy]

Got it, thanks. I already have the function to do the mapping from float to the range 0 to 15.

[makermelissa]

It's now merged in.