fix(pgw): add to menu

Author: RoRoJ

menu/navigation.json

@@ -3251,6 +3251,16 @@
                 "label": "API/CLI",
                 "slug": "api-cli"
               },
+              {
+                "items": [
+                  {
+                    "label": "Understanding v2",
+                    "slug": "understanding-v2"
+                  }
+                ],
+                "label": "Additional Content",
+                "slug": "reference-content"
+              },
               {
                 "label": "Troubleshooting",
                 "slug": "troubleshooting"