Add missing "JSON Entities" section title in rest-api-access.txt

Change-Id: I3f66431c5003b6f4a44869743e7b4a5300985c96
diff --git a/Documentation/rest-api-access.txt b/Documentation/rest-api-access.txt
index 42214fe..ffde05f 100644
--- a/Documentation/rest-api-access.txt
+++ b/Documentation/rest-api-access.txt
@@ -284,6 +284,9 @@
   }
 ----
 
+[[json-entities]]
+== JSON Entities
+
 [[access-section-info]]
 === AccessSectionInfo
 The `AccessSectionInfo` describes the access rights that are assigned