Know if argument was used without repeating option string

[RL-S]

Currently, the README says to use ArgumentParser::is_used(std::string_view) to check if an argument was used. This returns Argument::m_is_used.

I don't want to repeat a string. That's error-prone and can't be caught by the compiler if anything changes. I'd prefer the following pattern:

argparse::Argument& testArg = program.add_argument("-t", "--test").flag();
program.parse_args(argc, argv);
if ( testArg.is_used() ){
    ;/* do something */
}

and maybe let operator bool() redirect to that function, too:

if (testArg){/*.../*}

Is this intentionally disallowed? Would you be willing to accept a merge request to add this feature?