enablePositionalOptions(positional = true) {
    this._enablePositionalOptions = !!positional;
    return this;
  }
Enable positional options. Positional means global options are specified before subcommands which lets
subcommands reuse the same option names, and also enables subcommands to turn on passThroughOptions.
The default behaviour is non-positional and global options may appear anywhere on the command line.

@param {boolean} [positional]
@return {Command} `this` command for chaining