Implement custom code highlighter function

[kgabryje]

Usage:

Highlight codeblock:

{{< highlight >}}
<your code>
{{< /highlight >}}

Highlight code in specific language:

{{< highlight java >}}
<your java code>
{{< /highlight >}}

Add a wrapper with given class to code block:

{{< highlight class="runner-direct" >}}
<your code>
{{< /highlight >}}

Add a wrapper with given class to code block with language highlight:

{{< highlight class="runner-direct" lang="java" >}}
<your java code>
{{< /highlight >}}