Add backlink to index to backers.html and code sandbox

Author: marijnh

code/index.html

@@ -33,7 +33,7 @@
 </head>
 
 <article style="max-width: 50em;">
-  <h1>Code Sandbox<div style="font-size: 70%">Eloquent JavaScript</div></h2>
+  <h1>Code Sandbox<div style="font-size: 70%"><a class="subtlelink" href="../index.html">Eloquent JavaScript</a></div></h2>
 
   <p>You can use this page to download source code and solutions to
   exercises for the book Eloquent JavaScript, and to directly run code

html/backers.html

@@ -14,7 +14,7 @@
 </head>
 
 <article>
-  <h1>List of Backers<div style="font-size: 70%">Eloquent JavaScript</div></h2>
+  <h1>List of Backers<div style="font-size: 70%"><a class="subtlelink" href="index.html">Eloquent JavaScript</a></div></h2>
 
 <p>These are the kind souls who have contributed towards making the
 second edition of <a href="index.html">Eloquent JavaScript</a>

html/css/ejs.css

@@ -44,6 +44,11 @@ nav a {
   text-decoration: none !important;
 }
 
+a.subtlelink {
+  color: black !important;
+  text-decoration: none !important;
+}
+
 pre {
   padding: 5px 0 5px 15px;
   line-height: 1.35;