Supporting folders and subfolders in `Completions/`

Hi it would be very nice if Nova adds support, so that we can use Folders inside the Completions/ to organise our XML files. At the moment this is not possible.

This is handy, if the extension is adding/supporting multiple syntaxes in Syntaxes/, each having their own completions.

As a workaround I have had to just rename the file names, adding a prefix to keep the completions segregated and easy to find