fix(app): add og image

Author: danielroe

app/index.html

@@ -7,6 +7,14 @@
   <title>stackblitz.zip — Download StackBlitz projects instantly</title>
   <meta name="description"
     content="Download StackBlitz projects programmatically. No authentication or API keys required.">
+  <meta name="theme-color" content="#1389FD">
+  <meta property="og:image" content="/og-image.png">
+  <meta property="og:title" content="stackblitz.zip — Download StackBlitz projects instantly">
+  <meta property="og:description"
+    content="Download StackBlitz projects programmatically. No authentication or API keys required.">
+  <meta property="og:type" content="website">
+  <meta name="twitter:card" content="summary_large_image">
+  <meta name="twitter:image" content="/og-image.png">
   <link rel="icon" type="image/svg+xml" href="/favicon.svg">
   <link rel="stylesheet" href="/src/main.css">
 </head>