Update index.html

Author: mdmintz

coffee/index.html

@@ -3,6 +3,7 @@
   <link rel="icon" href="./assets/favicon.ico">
   <link rel="stylesheet" href="./assets/normalize.min.css">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <meta property="og:image" content="https://seleniumbase.github.io/cdn/img/coffee_cart.png">
   <title>Coffee Cart</title>
   <script async="" src="./assets/js"></script>
   <!-- Google tag (gtag.js) -->