Add meta tags

Author: lorensr

public/index.html

@@ -21,6 +21,25 @@
       Learn how to configure a non-root public URL by running `npm run build`.
     -->
 
+  <meta name="keywords" content="graphql apollo guide learn book course">
+  <meta name="description" content="📖 The complete GraphQL reference. By John Resig and Loren Sands-Ramshaw.">
+
+  <meta property="og:type" content="website">
+  <meta property="og:title" content="The GraphQL Guide">
+  <meta property="og:site_name" content="The GraphQL Guide">
+  <meta property="og:description" content="📖 The complete GraphQL reference. By John Resig and Loren Sands-Ramshaw.">
+  <meta property="og:url" content="https://graphql.guide">
+  <meta property="og:image" content="https://res.cloudinary.com/graphql/book" />
+  <meta property="og:image:type" content="image/png" />
+  <meta property="og:image:width" content="1971" />
+  <meta property="og:image:height" content="3087" />
+  <meta property="og:image:alt" content="The GraphQL Guide—book cover" />
+
+  <meta name="twitter:card" content="summary">
+  <meta name="twitter:site" content="@graphqlguide">
+  <meta name="twitter:title" content="The GraphQL Guide">
+  <meta name="twitter:description" content="📖 The complete GraphQL reference. By John Resig and Loren Sands-Ramshaw.">
+
   <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto:300,400,500">
 
   <title>The GraphQL Guide</title>