Beautifier for clang-format should tell the user what "File" means

1. Go to "Tools" -> "Options..." -> "Beautifier" -> "Clang Format".
2. If not done yet, select a Clang Format command.
3. Check "Use predefined style" and select "File".
   It's not obvious which file is meant by this. Users might expect an option to select a file (like I just did).

It would be good if there was some label or tooltip explaining which file be selected, so users don't have to search for this in the docs. Would it even make sense to add an option for selecting an arbitrary file?