code: function mdlink(anchor, href, title) {
    if (typeof anchor !== 'string') {
      throw new TypeError('markdown-link expects anchor to be a string.');
    }
    if (typeof href !== 'string') {
      throw new TypeError('markdown-link expects href to be a string.');
    }
  
    title = title ? ' "' + title + '"' : '';
    return '[' + anchor + '](' + href + title + ')';
  }
docs: ```js
  mdlink('foo', 'https://github.com/bar/foo', 'baz');
  //=> [foo](https://github.com/bar/foo "baz")
  
  mdlink('foo', 'https://github.com/bar/foo');
  //=> [foo](https://github.com/bar/foo)
  ```
  
  @param  {String} `anchor`
  @param  {String} `href`
  @param  {String} `title`
  @api public