Fix indentation of Compact URIs example

Author: theefer

core/index.html

@@ -1770,14 +1770,14 @@ <h2>Support for Compact URIs</h2>
 
   <figure><figcaption>A JSON-LD Compact URI definition</figcaption>
 <pre class="example highlight json">{
-"@context": {
-"ex": "http://example.org/",
-"term": {
-  "@type": "id",
-  "@id": "ex:term"
-}
-},
-"term": "ex:Foo"
+  "@context": {
+    "ex": "http://example.org/",
+    "term": {
+      "@type": "id",
+      "@id": "ex:term"
+    }
+  },
+  "term": "ex:Foo"
 }</pre></figure>
 
   <p>