Add RAR compression check and warning in submission system

[mahirst]

RAR is a proprietary compression format that we should not host on our open-access platform. We have already updated our language on the help pages following #3754.

It would be useful to have a function in the Upload files part of the submission system that checks for .rar files and generates a warning that we do not accept this compression file type because it is proprietary. Preferably, the system would block the upload of these types of files.

Potential warning message to use:

Warning: RAR is a proprietary compression format that is not universally accessible. Please use an open-access format, such as TAR.GZ, 7Z, or ZIP.

[ahamelers]

Is it okay to have this in the new submission system only or is this needed urgently?