import { Command } from "https://dotland.deno.dev/x/cliffy@v0.16.0/command/mod.ts";
Add a new option.
Parameters
Flags string like: -h, --help, --manual requiredArg:string [optionalArg: number] [...restArgs:string]
optional
opts: ICommandOption | IFlagValueHandlerFlag options or custom handler for processing flag value.