Add deprecation warning to release-1.6

Author: chenopis

_config.yml

@@ -43,6 +43,9 @@ defaults:
           githubbranch: "v1.4.12"
           docsbranch: "release-1.4"
           url: https://v1-4.docs.kubernetes.io/docs/
+      deprecated: true
+      currentUrl: https://kubernetes.io/docs/home/
+      nextUrl: http://kubernetes-io-vnext-staging.netlify.com/
   -
     scope:
       path: "docs"

_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+        Documentation for Kubernetes {{ page.version}} is no longer actively maintained.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 %}

_layouts/docwithnav.html

@@ -35,6 +35,8 @@ <h5>{{ toc.abstract }}</h5>
   </div>
 </section>
 
+{% include deprecation-warning.html %}
+
 <section id="encyclopedia">
   <div id="docsToc">
         <div class="pi-accordion">

css/deprecation-warning.css

@@ -0,0 +1,6 @@
+.deprecation-warning {
+    padding: 20px;
+    margin: 20px 0;
+    border-radius: 3px;
+    background-color: #eeeeee;
+}

index.html

@@ -21,6 +21,8 @@ <h5>Automated container deployment, scaling, and management</h5>
     <!--</div>-->
 </section>
 
+{% include deprecation-warning.html %}
+
 <!--  OCEAN NODES  -->
 <section id="oceanNodes">
     <main>