User guide: hide night mode toggle from screenreaders

Author: Frenzie

user_guide/en.html

@@ -803,7 +803,7 @@
 
 <div class="outer-container">
 
-    <label class="switch">
+    <label class="switch" aria-hidden="true">
         <input type="checkbox" id="theme-switcher">
         <span class="slider round"></span>
     </label>