Create highlight groups for string literal prefixes (f, r, b, …) and (keyword) args

[sscherfke]

In sublime text, the string literal prefixes (e.g, the "f" in f'a string') and function arguments (names and values) are separate highlight groups:

It would be nice if we could have this in vim, too. :)

[nfnty]

Certainly could be added. Send a PR if you're interested in contributing!

[qwenger]

I second this. As an addendum, it would also be nice to have groups for the quotes themselves, like the default python.vim does (pythonQuotes, https://github.com/vim/vim/blob/master/runtime/syntax/python.vim#L137).