Pywhat should accept multiple files as input

Pywhat supports files and folders, but it does not allow passing several files as arguments:
`$ pywhat file1 file2 file3` results in
`Error: Got unexpected extra arguments (file2 file3)`

Start at pywhat's command-line argument handling and trace how file and folder inputs are parsed. Reproduce the reported command with several files, then verify that multiple file arguments are accepted while existing single-file and folder inputs continue to work.

Written by the indexing model from the issue text.