message: add onmissing args method to cmd signature
diff: @@ -105,6 +105,9 @@ export class Command implements CommandOptions {
  /** Method called when the command errors */
  onError(ctx: CommandContext, error: Error): any {}
  + /** Method called when there are missing arguments */
  + onMissingArgs(ctx: CommandContext): any {}
  +
  /** Method executed before executing actual command. Returns bool value - whether to continue or not (optional) */
  beforeExecute(ctx: CommandContext): boolean | Promise<boolean> {
  return true
  