Added type hints (Issue #8)

[jreanah]

Added type hints to functions and methods in the adafruit_display_notification directory.

[jreanah]

@tekktrik

[jposada202020]

@jreanah The CI is not running automatically in your case, please feel free to ping me in case you need that I start the workflow. Thanks for your contribution :)

[tekktrik]

It looks like the CI had some issues. You can use pre-commit to fix them and then push the changes. Here's the information on installing and using pre-commit: https://learn.adafruit.com/creating-and-sharing-a-circuitpython-library/check-your-code

[tekktrik]

See above :)

[FoamyGuy]

The typing for this repo was completed in #14