Add listings

Listing_10.13.html

@@ -14,10 +14,18 @@
     <div class="container">
       <div class="content">
 
-  <h1>Palindrome Detector</h1>
-
-  <p>This will be the palindrome detector.</p>
+  <h1>About</h1>
 
+  <p>
+    This site is the final application in
+    <a href="https://www.learnenough.com/python-tutorial"><em>Learn Enough Python
+    to Be Dangerous</em></a>
+    by <a href="https://www.michaelhartl.com/">Michael Hartl</a>,
+    a tutorial introduction to the
+    <a href="https://www.python.org/">Python programming language</a> that
+    is part of
+    <a href="https://www.learnenough.com/">LearnEnough.com</a>.
+  </p>
       </div>
     </div>
   </body>