text: Title: Decide and document XDG media type
  Body: I've created an issue to XDG mimetypes repo about adding a mediatype for robot framework
  https://gitlab.freedesktop.org/xdg/shared-mime-info/-/issues/198
  
  I think having mediatype `text/robotframework` would be ok. This means any text editor would know it's a text file, and those which have syntax highlight etc. support for Robot files can enable that as well.
  
  