Feature request: method to handle command exection

[zefir-git]

It would be nice if you could define a command handler directly on the Command instance, removing the need to use ProgramArgs and specify handling for everything there. That would allow sub-commands to be in their own modules and have their execution logic locally, rather than having everything in a single file.

For example:

new Command("foo", "bar")
    /* … */
    .action((arguments, options) => {
        /* … */
    });

Or subcommands could even be used as their own classes that extend Command.