UI Enhancements: URLs, Web-font path and CSS fixes (#661)

- Only the external links are set to open in new windows/tab
- Fixed incorrect web-font paths being called for preload. 
- Minor CSS transition fixes.
- Conditionally called the search modal's keyboard events.

source/_static/js/main.js

@@ -361,4 +361,18 @@ window.addEventListener("DOMContentLoaded", (event) => {
       });
     }
   })();
+
+  // --------------------------------------------------
+  // Handle internal and external links
+  // --------------------------------------------------
+  (function () {
+    const links = document.querySelectorAll(".content__main a.external");
+    if(links.length > 0) {
+      links.forEach((item) => {
+        item.setAttribute("target", "_blank");
+        item.setAttribute("rel", "noopener");
+        item.setAttribute("rel", "noreferrer");
+      });
+    }
+  })();
 });