Add link to Playground from the main example.

Author: BigBlueHat

index.liquid

@@ -21,7 +21,11 @@ masthead:
     </p>
   </div>
   <div class="eight wide column">
-    <pre class="ui segment">{
+    <div class="ui segment">
+      <a class="ui top right attached primary label"
+        href="/playground/#startTab=tab-expanded&json-ld=%7B%22%40context%22%3A%22https%3A%2F%2Fjson-ld.org%2Fcontexts%2Fperson.jsonld%22%2C%22%40id%22%3A%22http%3A%2F%2Fdbpedia.org%2Fresource%2FJohn_Lennon%22%2C%22name%22%3A%22John%20Lennon%22%2C%22born%22%3A%221940-10-09%22%2C%22spouse%22%3A%5B%22http%3A%2F%2Fdbpedia.org%2Fresource%2FYoko_Ono%22%2C%22http%3A%2F%2Fdbpedia.org%2Fresource%2FCynthia_Lennon%22%5D%7D"
+        >Open in Playground</a>
+      <pre style="margin: 0 !important;">{
   "<span style="color: rgb(255, 122, 0);">@context</span>": "<a href="https://json-ld.org/contexts/person.jsonld">https://json-ld.org/contexts/person.jsonld</a>",
   "<span style="color: rgb(255, 122, 0);">@id</span>": "<a href="http://dbpedia.org/resource/John_Lennon">http://dbpedia.org/resource/John_Lennon</a>",
   "<span style="color: rgb(255, 122, 0);">name</span>": "<span style="color: rgb(0, 148, 0);">John Lennon</span>",
@@ -30,7 +34,7 @@ masthead:
     "<a href="http://dbpedia.org/resource/Yoko_Ono">http://dbpedia.org/resource/Yoko_Ono</a>",
     "<a href="http://dbpedia.org/resource/Cynthia_Lennon">http://dbpedia.org/resource/Cynthia_Lennon</a>"
   ]
-}</pre>
+}</pre></div>
   </div>
   <div class="justified four wide column">
     <h2><img class="ui micro inline image" src="images/json-ld-data-32.png" alt="JSON-LD logo"> JSON-LD</h2>