Adding preconnect for the socket (#1075)

* Update index.html

* fix formatting

public/index.html

@@ -78,6 +78,11 @@
       type="font/ttf"
       crossorigin="anonymous"
     />
+    <link
+      href="https://excalidraw-socket.herokuapp.com/socket.io"
+      rel="preconnect"
+      crossorigin="anonymous"
+    />
 
     <link rel="manifest" href="manifest.json" />
     <link