Fix: Clean SVG and include external dark mode script

Author: DivyaSimhadri1004

doc/_themes/sphinx13/layout.html

@@ -112,8 +112,7 @@ <h3>{{ _('On this page') }}</h3>
   <symbol id="github" viewBox="0 0 16 16">
     <title>GitHub</title>
     <path fill-rule="evenodd"
-      d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 
-      5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82
+      d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82
       -.01-1.49-2.01.37-2.53-.49-2.69-.94
       -.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52
       -.01-.53.63-.01 1.08.58 1.23.82