Add deprecation warning to release-1.6

_includes/deprecation-warning.html

@@ -0,0 +1,12 @@
+{% if page.deprecated %}
+<section id="deprecationWarning">
+  <main>
+    <div class="content deprecation-warning">
+      <h3>
+        Documentation for Kubernetes {{ page.version}} is no longer actively maintained. The version you are currently viewing is a static snapshot.
+        For up-to-date documentation, see the <a href="{{ page.currentUrl }}">latest</a> version.
+      </h3>
+    </div>
+  </main>
+</section>
+{% endif %}

_includes/head.html

@@ -7,6 +7,7 @@
     <link rel="stylesheet" type="text/css" href="/css/styles.css">
     <link rel="stylesheet" type="text/css" href="/css/jquery-ui.min.css">
     <link rel="stylesheet" type="text/css" href="/css/sweetalert.css">
+    {% if page.deprecated %}<link rel="stylesheet" type="text/css" href="/css/deprecation-warning.css">{% endif %}
     {% if page.class == "gridPage" %}<link rel="stylesheet" type="text/css" href="/css/gridpage.css">{% endif %}
 
     {% if page.description %}