Add link to self-healing SIG documentation

The self-healing SIG documentation is in its early stages, but already
includes some practical information which certain operators may find
useful.

Linking from the index also helps promote the visibility of the SIG,
which could help encourage more involvement from operators, which
would in turn help drive development, reducing the inertia of the
current chicken-and-egg bootstrapping challenge we face.

Change-Id: I9821c1a228a35a729ea4f101b29f2dcf8cbbf152
Story: 2001628
Task: 24545

www/static/common/css/font-awesome-additions.css

@@ -0,0 +1,3 @@
+.fa-users-cog:before {
+  content: "\f509";
+}

www/stein/index.html

@@ -68,6 +68,11 @@
         <a href="language-bindings.html">Language Bindings and Python Clients</a>
         <p>Documentation for the OpenStack Python bindings and clients</p>
       </div>
+      <div class="docs-link-sections">
+        <h3 id="services-libraries"><i class="fa fa-users-cog"></i>SIG-specific documentation</h3>
+        <a href="/self-healing-sig/">Self-healing SIG documentation</a>
+        <p>Self-healing use cases and implementation details</p>
+      </div>
       <div class="docs-link-sections">
         <h3 id="doc-contrib-guides"><i class="fa fa-pencil"></i>Contributor Guides</h3>
         <a href="/doc-contrib-guide/index.html">OpenStack Documentation Contributor Guide</a>

www/templates/css.tmpl

@@ -10,6 +10,7 @@
     <!-- Fonts -->
     <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.6.3/css/all.css" integrity="sha384-UHRtZLI+pbxtHCWp1t77Bi1L4ZtiqrqD80Kn4Z8NTSRyMA2Fd33n5dQ8lWUE00s/" crossorigin="anonymous">
     <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.6.3/css/v4-shims.css">
+    <link href="{{ CSSDIR }}font-awesome-additions.css" rel="stylesheet">
 
     <!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries -->
     <!-- WARNING: Respond.js doesn't work if you view the page via file:// -->