Add categories to cookbook

source/_includes/asides/cookbook_navigation.html

@@ -0,0 +1,25 @@
+<section class="aside-module grid__item one-whole lap-one-half">
+  {% include edit_github.html %}
+  {% assign cookbook = site.cookbook | sort: 'title' %}
+
+  <div class='section'>
+    <a href='/cookbook'>Back to the cookbook</a>
+  </div>
+
+  <div class='section'>
+    <h1 class="title delta">{{page.ha_category}}</h1>
+    <ul class='divided'>
+      {% for recipe in cookbook %}
+        {% if recipe.ha_category == page.ha_category %}
+          <li>
+            {% if recipe.url == page.url %}
+              {{recipe.title}}
+            {% else %}
+              <a href='{{recipe.url}}'>{{recipe.title}}</a>
+            {% endif %}
+          </li>
+        {% endif %}
+      {% endfor %}
+    </ul>
+  </div>
+</section>

source/_includes/site/sidebar.html

@@ -2,6 +2,8 @@
   {% assign url_parts = page.url | split: '/' %}
   {% if url_parts[1] == 'components' %}
     {% include asides/component_navigation.html | compact_newlines %}
+  {% elsif url_parts[1] == 'cookbook' %}
+    {% include asides/cookbook_navigation.html | compact_newlines %}
   {% else %}
     {% include asides/about.html %}