Refactor font loading JS

Fixes font loading issues.

content.js

@@ -1,9 +1,8 @@
 /* This runs after a web page loads */
-function addStylesheetURL(url) {
-  var link = document.createElement('link');
-  link.rel = 'stylesheet';
-  link.href = url;
-  document.getElementsByTagName('head')[0].appendChild(link);
-}
-
-addStylesheetURL("https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@400;600;700&family=Press+Start+2P&display=swap");
+var getHeader = document.getElementsByTagName('head').item(0);
+var linkStyle = document.createElement("link");
+var url = "https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@400;600;700&family=Press+Start+2P&display=swap";
+linkStyle.href = url;
+linkStyle.rel = 'stylesheet';
+linkStyle.type = "text/css"; 
+getHeader.appendChild(linkStyle);