Allow using different single letter shortcut for `--help` option (e.g. `-?`)

[benmccann]

SvelteKit needs -h for host, but currently can't use it because sade is hardcoding it to --help (sveltejs/kit#1432)

I'm used to -h for host. E.g. that's what the mysql and psql command-line clients do. They use -? for help