Add placeholder for job managed-by label docs

Author: mimowo

content/en/docs/reference/command-line-tools-reference/feature-gates/job-managed-by-label.md

@@ -0,0 +1,14 @@
+---
+title: JobManagedByLabel
+content_type: feature_gate
+
+_build:
+  list: never
+  render: false
+
+stages:
+  - stage: beta
+    defaultValue: false
+    fromVersion: "1.30"
+---
+Allows to delegate reconciliation of a Job object to an external controller.