Fix: Clean SVG and include external dark mode script

Author: DivyaSimhadri1004

doc/_themes/sphinx13/layout.html

@@ -112,20 +112,19 @@ <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
-      -.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
-      .72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07
-      -1.78-.2-3.64-.89-3.64-3.95
-      0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12
-      0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27
-      .68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82
-      .44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15
-      0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48
-      0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 
-      8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z">
+      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 1.23.82.72 1.21 1.87.87 
+      2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 
+      0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 
+      0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27 
+      .68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82 
+      .44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 
+      0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 
+      0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38 
+      A8.013 8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z">
     </path>
   </symbol>