serve: Fix corner cases where the pipeline doesn't run correctly. * When `chef serve` is run before the `assets` folder is created, monitor that folder suddenly appearing and rebuild the pipeline. * Do the same when the `config.yml` file has changed.

{% extends "section-page.html" %}

{% block header %}
<header class="documentation">
    <h1>{{ page.title }}</h1>
</header>
{% endblock %}