Add version 1.13.1 to the change log

Author: jgonggrijp

index.html

@@ -2718,6 +2718,22 @@ <h2 id="notes">Notes</h2>
 
       <h2 id="changelog">Change Log</h2>
 
+      <p id="1.13.1">
+        <b class="header">1.13.1</b> &mdash; <small><i>April 15, 2021</i></small> &mdash; <a href="https://github.com/jashkenas/underscore/compare/1.13.0...1.13.1">Diff</a> &mdash; <a href="https://cdn.rawgit.com/jashkenas/underscore/1.13.1/index.html">Docs</a><br />
+        <ul>
+          <li>
+            Restores the <tt>underscore.js</tt> alias committed to the GitHub
+            repository.
+          </li>
+          <li>
+            Adds some build clarifications to the documentation.
+          </li>
+          <li>
+            No code changes.
+          </li>
+        </ul>
+      </p>
+
       <p id="1.13.0">
         <b class="header">1.13.0</b> &mdash; <small><i>April 9, 2021</i></small> &mdash; <a href="https://github.com/jashkenas/underscore/compare/1.13.0-3...1.13.0">Diff</a> &mdash; <a href="https://cdn.rawgit.com/jashkenas/underscore/1.13.0/index.html">Docs</a><br />
         <ul>