[FEATURE] Use type hints in af_colours

[nickhenden]

Preliminary Checks

• I have searched existing issues to ensure this feature hasn't been requested before

Proposed Solution

Add type hints to the code in src\afcharts\af_colours.py

[mylsklaark]

Having some challenges with this one. Mypy is failing because some functions can return two different kinds of lists, but the type checker wants one clear type at each step. In hex mode the code returns text colours, and in rgb mode it returns number tuples, and some functions put both possibilities into the same variable. We could get around this by casting, or by some small tweaks to the functions so that the same variable can't be both things.

[nickhenden]

@mylsklaark I'm afraid this isn't my area of expertise but I'll happily take a look. Do you have a branch I could look at for starters?

Have you tried using the | operator? e.g. does list[str] | list[Tuple[int]] work (if that's even allowed)?

Also out of interest, does mypy stop complaining if you set the type to Any?

[mylsklaark]

I do have a branch, I’ll share it before the week’s out! I’ll try and give your suggestion a spin, too.