argparse: undocumented `nargs` constants `ONE_OR_MORE`, `OPTIONAL`, `PARSER`, `REMAINDER`, `ZERO_OR_MORE`, `SUPPRESS`

[rindeal]

Concerning the possible values of the nargs parameter of add_argument().

The following values are already described in the documentation, so only a mention of the constants is needed:

• OPTIONAL = ?
• ZERO_OR_MORE = *
• ONE_OR_MORE = +

The following constants and their values do not seem to be documented anywhere:

• PARSER
• REMAINDER

SUPPRESS constant was documented for help parameter in https://github.com/python/cpython/issues/53595, but not for nargs.