docs: fix missing syntax (#417)

docs/web-integration.md

@@ -142,8 +142,8 @@ embed.createConfiguration({
     // ...
     {
       name: 'piechart',
-      load: () = Promise.resolve(piechart)
+      load: () => Promise.resolve(piechart)
     }
-  ];
-}
+  ]
+});
 ```