add navigation html template for docs

Author: joonlabs

docs/_include/navigation.html

@@ -0,0 +1,38 @@
+<!-- This finds the current page so it can be highlighted. -->
+
+{% for entry in site.data.navigation %}
+{% capture fullurl %}{{ site.baseurl }}{{ entry.url }}{% endcapture %}
+{% if fullurl == page.url %}
+{% assign current_page = fullurl %}
+{% break %}
+{% elsif page.url contains fullurl %}
+{% assign current_page = fullurl %}
+{% endif %}
+{% endfor %}
+
+<!-- Then we build the nav bar. -->
+<nav>
+    <ul>
+        {% for entry in site.data.navigation %}
+        {% if entry.url == current_page %}
+        {% assign current = ' class="current"' %}
+        {% else %}
+        <!-- We have to declare it 'null' to ensure it doesn't propagate. -->
+        {% assign current = null %}
+        {% endif %}
+        {% assign sublinks = entry.sublinks %}
+        {% if sublinks %}
+        <li{{ current }}>
+        <a href="{{ site.baseurl }}{{ entry.url }}">{{ entry.title }}</a>
+        <ul>
+            {% for sublink in sublinks %}
+            <li><a href="{{ site.baseurl }}{{ sublink.url }}">{{ sublink.title }}</a></li>
+            {% endfor %}
+        </ul>
+        </li>
+        {% else %}
+        <li{{ current }}><a href="{{ site.baseurl }}{{ entry.url }}">{{ entry.title }}</a></li>
+        {% endif %}
+        {% endfor %}
+    </ul>
+</nav>