Update CodeMirror dep to v5.42.2

Affects Code and Markdown section types

gui/public/codemirror/mode/stex/index.html

@@ -9,7 +9,7 @@
 <script src="stex.js"></script>
 <style>.CodeMirror {background: #f8f8f8;}</style>
 <div id=nav>
-  <a href="http://codemirror.net"><h1>CodeMirror</h1><img id=logo src="../../doc/logo.png"></a>
+  <a href="https://codemirror.net"><h1>CodeMirror</h1><img id=logo src="../../doc/logo.png"></a>
 
   <ul>
     <li><a href="../../index.html">Home</a>
@@ -103,6 +103,12 @@
       var editor = CodeMirror.fromTextArea(document.getElementById("code"), {});
     </script>
 
+    <p>sTeX mode supports this option:</p>
+    <d1>
+      <dt><code>inMathMode: boolean</code></dt>
+      <dd>Whether to start parsing in math mode (default: <code>false</code>).</dd>
+    </d1>
+
     <p><strong>MIME types defined:</strong> <code>text/x-stex</code>.</p>
 
     <p><strong>Parsing/Highlighting Tests:</strong> <a href="../../test/index.html#stex_*">normal</a>,  <a href="../../test/index.html#verbose,stex_*">verbose</a>.</p>