Allow returning of path_style from path_display function

[sarmong]

Is your feature request related to a problem? Please describe.
I like filename_first option of path_display, however I also want to be able to modify the path. So, I need to pass a function to path_display. However, I am not able to replicate the way filename_first looks, because I cannot pass TelescopeResultsComment hl group.

Describe the solution you'd like
Allow returning optional second value from path_display function.

[sarmong]

I am also thinking now that maybe another approach for this problem is to make a function part of the list for path_display?

So, one could do something like this:

path_display = {
 'filename_first',
 function(_, path)
   return string.gsub(path, 'substr', 'mystr')
 end
}

However, I would say that returning path_style is still useful. This would just complement it.

[jamestrew]

Yeah letting users return an optional table of highlights is probably a good idea.
I'll take a look at your PR.