Adding permutator feature for usernames (#1575)

* Adding permutator feature for usernames
("", "_", "-", ".") when id_type == username

File : maigret/permutator.py

Arg : --permute

For now, only permute from 2 elements and doesn't return single elements (element1, _element1, element1_,  element2, _element2, ...). 12 permuts for 2 elements.

To return single elements as well, Permute(usernames).gather(method="all"), but not implemented in maigrat.py. 18 permuts for 2 elements. Should we ? With another argument ?

* Update test_cli.py

permute arg added

tests/test_cli.py

@@ -23,6 +23,7 @@ DEFAULT_ARGS: Dict[str, Any] = {
     'no_progressbar': False,
     'parse_url': '',
     'pdf': False,
+    'permute': False,
     'print_check_errors': False,
     'print_not_found': False,
     'proxy': None,