Add digits to keyword character set

[alextes]

@paluh if I understand correctly this would change how Vim reacts to motions as digits would become keywords? Can you perhaps open an issue explaining the problem first?

I'd love to just give you access and let you maintain but I don't have that power 😅 , so until someone forks I'd at least like to understand what I'm merging 😬 .

[paluh]

Hi @alextes,

This PR extends character set for identifiers so we can import symbols which contain digits like foldMap1. Currently this is impossible.

[alextes]

@paluh aaaah, great! Merged!