* Find icons using Qt's u""_s string literals
* Only look for exactly matching icon names or for icon names followed
  by a dash so that we also include the more generic icon variants
  because sometimes there is no icon for the more specific full icon
  name. Moreover, this excludes icons with short names which happen to
  match the start of a used icon.
* Look for exact matches when checking for already included icons
* Speed it up by grepping all files only twice recursively