Make IDLE .desktop support Python MIME files
Indicate in the .desktop file for IDLE that it is capable of accepting file arguments at the command line and that it supports the Python MIME. This allows desktop environments to identify IDLE as a possible application for opening Python files.
Fedora carries a .desktop file similar to this for this reason: https://src.fedoraproject.org/cgit/rpms/python3.git/tree/idle3.desktop
P.S. This is my first contribution to a debian packaging repository, so apologies if this is incorrect in any way.