title: TinyMCE format for multiple elements/selectors
body: <p>I want to add a custom format to TinyMCE, that will add a custom class to any heading element selected, or even any element selected at all.</p>
  
  <p>Declaring format for only a single element/tag <strong>works fine</strong>. In the following example, if your selection is within the <code>H1</code>, this format will add a class to it.<br>
  However, if your selection is within the <code>H3</code> element, the element will be converted to <code>H1</code> alongside receiving a custom class.</p>
  
  <pre><code>array(
   'title' =&gt; 'Custom Style',
   'inline' =&gt; '',
   'block' =&gt; 'h1',
   'selector' =&gt; '',
   'classes' =&gt; 'custom-class'
  )
  </code></pre>
  
  <p>I tried using <code>,</code> and <code>|</code> separated lists of elements, or even completely empty but everything throws an error:</p>
  
  <pre><code>'block' =&gt; 'h1,h2,h3,h4,h5,h6'
    // or
  'selector' =&gt; 'h1|h2|h3|h4|h5|h6'
    // or
  'block' =&gt; ''
  'selector' =&gt; ''
  </code></pre>
  
  <hr>
  
  <p>Is it possible to support multiple block elements, or simply add the class to the selected element - no matter what it is?</p>