Add discouraged features tab

site/_includes/feature_list_views.njk

@@ -5,6 +5,7 @@
   <li><a href="/widely-available" class="baseline-high">Widely available</a></li>
   <li><a href="/limited-availability" class="baseline-false">Limited availability</a></li>
   <li><a href="/one-missing-engine" class="baseline-false">One missing engine</a></li>
+  <li><a href="/discouraged" class="discouraged-info">Discouraged</a></li>
   {% for browser in browsers %}
     <li><a href="/browsers/{{ browser.id | slugify }}/">{{ browser.name }}</a></li>
   {% endfor %}

site/discouraged.njk

@@ -0,0 +1,22 @@
+---
+title: Discouraged features
+layout: layout.njk
+---
+
+<main class="explore-features">
+  {% include "feature_list_views.njk" %}
+
+  <h1>{{ title }}</h1>
+
+  <p>Using the following features is discouraged, even if they're still implemented in browsers, because standards bodies and/or browser implementers have agreed that they should not be used.</p>
+
+  <ul class="features">
+    {% for feature in allFeatures %}
+      {% if feature.discouraged %}
+        <li>
+          {% include "feature_short.njk" %}
+        </li>
+      {% endif %}
+    {% endfor %}
+  </ul>
+</main>