<!doctype html>
<html>
  <head>
    <link rel="stylesheet" href="lib/codemirror.css">
    <link rel="stylesheet" href="source-editor.css">
    <script src="lib/codemirror.js"></script>
    <script src="lib/util/loadmode.js"></script>
    <script src="source-editor.js"></script>
  </head>
  <body>
  </body>
</html>
<!doctype html>
<html>
  <head>
    <link rel="stylesheet" href="lib/codemirror.css">
    <link rel="stylesheet" href="source-editor.css">
    <script src="lib/codemirror.js"></script>
    <script src="lib/util/loadmode.js"></script>
    <script src="lib/util/overlay.js"></script>
    <script src="source-editor.js"></script>
  </head>
  <body>
  </body>
</html>
Add script tag for overlay.js needed by gfm mode
Add script tag for overlay.js needed by gfm mode