import { args } from "https://deno.land/x/feomasto@v0.1.0/priv/deps.ts";
const { FlaggedCommand } = args;
Add a flag parser on top of existing command parser
type
<MainVal, NextKey extends string, NextVal, ErrList extends readonly ParseError[]>(main: Command<CommandReturn.Main<MainVal>, ErrList>, flag: FlagType<NextKey, NextVal>) => Command<FlaggedCommandReturn<MainVal, NextKey, NextVal>, ErrList | readonly [ParseError]>