Update en.json

docs/en/en.json

@@ -1419,6 +1419,10 @@
                         "path": "/manuals/extensions-build-variants",
                         "name": "Build Variants"
                     },
+                    {
+                        "path": "/manuals/app-manifest",
+                        "name": "App Manifests"
+                    },
                     {
                         "path": "/manuals/extensions-manifest-merge-tool",
                         "name": "Manifest Merging"