message: docs(aio): add changelog, as hidden, to navigation
  This ensures that the changelog page is formatted correctly.
  Closes
  PR Close
diff: "title": "API",
  "tooltip": "Details of the Angular classes and values.",
  "url": "api"
  + },
  + {
  + "url": "guide/change-log",
  + "title": "Change Log",
  + "tooltip": "Angular Documentation Change Log",
  + "hidden": true
  }
  ],
  