I'm currently experiencing problems getting the source code highlighting to work with https://github.com/markedjs/marked
The reason is that Marked outputs the following structure:
```html
<pre><code class="language-js">const hello = 'world';</code></pre>
```
and the current selector expects the `pre` tag to have a `lang` attribute.
This PR splits the forwarding of the `lang` attribute to a class and the code that initialise the highlighting for each block. It will try to initialise the highlighting for every `code` block that is inside a `pre` tag.
580de0be1f