doc/tutorial/basics: fix link and JSON results

Change-Id: I9908521f22949429ac14ec9d60fb08602adc0eb6
diff --git a/doc/tutorial/basics/fold.md b/doc/tutorial/basics/fold.md
index 4e8fa8e..952c240 100644
--- a/doc/tutorial/basics/fold.md
+++ b/doc/tutorial/basics/fold.md
@@ -13,9 +13,11 @@
 
 <!-- JSON result -->
 ```json
-"outer": {
-    "middle": {
-        "inner": 3
+{
+    "outer": {
+        "middle": {
+            "inner": 3
+        }
     }
 }
 ```
\ No newline at end of file