title: disable convert font style, header, image
body: <p>How to only allow change line and link, auto link. disable all other features with showdown <a href="https://github.com/showdownjs/showdown" rel="nofollow">https://github.com/showdownjs/showdown</a>  ?<br>
  (like font style, header, list style, image ...)<br>
  I saw there is subParsers folder, is there a way to use that, I can choose to parse what I want, like </p>
  
  <pre><code>var html = showdown.subParser('autoLink');
  html = showdown.subParser('..')
   ...
  </code></pre>
  
  <p>js</p>
  
  <pre><code>var showdown  = require('showdown');
  
  var converter = new showdown.Converter();
  converter.setOption('noHeaderId', true);
  converter.setOption('ghCodeBlocks', false);
  converter.setOption('literalMidWordUnderscores', true);
  
  
  var html = converter.makeHtml(d);
  console.log(html)
  </code></pre>
  
  <p><a href="https://jsfiddle.net/60bjuob8/4/" rel="nofollow">https://jsfiddle.net/60bjuob8/4/</a></p>
  
  <pre><code>showdown.extension('myext', function() {
    return [{ type: 'lang', regex: /^#/gm, replace: '\\#' }];
  });
  
  $('.convert').on('click', function() {
    var cnv = new showdown.Converter({extensions: ['myext']});
    var txt = $('#foo').val();
    var html = cnv.makeHtml(txt);
    $('#bar').val(html);
  });
  </code></pre>