message: docs(aio): put structural directives back in the nav
  PR Close
diff: "title": "Attribute Directives",
  "tooltip": "Attribute directives attach behavior to elements."
  },
  + {
  + "url": "guide/structural-directives",
  + "title": "Structural Directives",
  + "tooltip": "Structural directives manipulate the layout of the page."
  + },
  {
  "url": "guide/pipes",
  "title": "Pipes",
  