Update base.html

Add missing semicolon on line preceding `data` in CSP

src/docs/_templates/base.html

@@ -28,7 +28,7 @@
         <meta http-equiv="Content-Security-Policy" 
             content="
             default-src 'self'; 
-            child-src 'self'
+            child-src 'self';
             data: https://*.github.io;
             img-src 'self' https://*.cookielaw.org https://*.onetrust.com;
             data: https://*.github.io https://github.com https://*.githubusercontent.com;