Add type hints

[Conengmo]

• Add type hints to all modules in Branca.
• Make sure Mypy passes.

Contains some (internally) functional changes as well:

• Alter _parse_hex to output RGBA floats directly. We only use that function inside of _parse_color, which needs RGBA floats as output.
• No longer have bytes as accepted type for color strings. That's a remnant from the Python 2 times.
• Merge duplicate code in Link, JavascriptLink and CssLink.

Do separately later:

• make subclasses of Figure use the same types for width and height. Also a separate PR I think. Would be easiest to have _parse_size just return a single string.
• simplify the _camelify function. Is it even needed?
• remove get_templates

[Conengmo]

@ocefpaf would you mind taking a look at this PR at some time? No hurry. I know it's pretty big, but I don't know how to do it otherwise, it's just a lot of type hints. I'm open to suggestions! I'm asking you since you also did python-visualization/folium#1677.

[ocefpaf]

@ocefpaf would you mind taking a look at this PR at some time? No hurry. I know it's pretty big, but I don't know how to do it otherwise, it's just a lot of type hints. I'm open to suggestions! I'm asking you since you also did python-visualization/folium#1677.

Sure. I don't have a lot of experience but we can try to run mypy here to check things? I'll see what we can do. There are also some pre-commits that can help.

PS: we need to fix a conflict but I'm looking at it now.

[ocefpaf]

Ha! You are always one (many actually) step ahead of me.

[Conengmo]

Thanks Filipe, much appreciated! I’ll solve the merge conflict before merging. Good idea to add a precommit config as well, I’ll do that in a separate PR.