feat: folder_browser with more filetypes

[fdschmidt93]

This allows the following:

:lua require "telescope".extensions.file_browser.file_browser { types = {"file", "directory"}}

now makes the folder_browser show both files and directories (default: types = { "directory" }) and you can switch to the folder of a particular file.

I think the feature is actually ready to be merged, but I'm not so happy about the types opt. Either I come up with concise and clear names by {file, folder}_browser, respectively, or we will be needing some separation via tables or something. Sadge.

folder_browser_files.mp4

[windowsrefund]

This seems like it would be a great solution for #176.