Use file icons in Merge Request View

This is a design/UX proposal as I was just working on the collapse icon for the new refactored MR page. So I gave it a try to add the FileIcon component from the Web IDE to the MR to create a nicer overview of the actual files and it makes it in my experience much faster to scan a couple of files.

Take a look and give the MR a try:

P.S.: If we like it we just need to merge as it is already implemented 😆