Allows to write custom code blocks:
```
```mermaid height=200,foo=bar
test
```
```
Which will then get converted to:
```
<pre data-code-wrap="mermaid" data-code-height="200" data-code-foo="bar">
<code class="lang-nohighlight">
test
</code>
</pre>
```
New site settings:
enable_markdown_linkify: which is default on, auto links https:// and http:// and mail://
markdown_linkify_tlds: which allows control of what tlds get autolinked for cases such as www.site.com, default is com|net|gov
