zerolinelayer description: Add note that it doesn't work in combination with zorder.

Author: my-tien

src/plots/cartesian/layout_attributes.js

@@ -1025,7 +1025,8 @@ module.exports = {
             'Sets the layer on which this zeroline is displayed.',
             'If *above traces*, this zeroline is displayed above all the subplot\'s traces',
             'If *below traces*, this zeroline is displayed below all the subplot\'s traces,',
-            'but above the grid lines.'
+            'but above the grid lines. Limitation: *zerolinelayer* currently has no effect',
+            'if the *zorder* property is set on any trace.'
         ].join(' ')
     },
     zerolinewidth: {

test/plot-schema.json

@@ -14960,7 +14960,7 @@
      "valType": "color"
     },
     "zerolinelayer": {
-     "description": "Sets the layer on which this zeroline is displayed. If *above traces*, this zeroline is displayed above all the subplot's traces If *below traces*, this zeroline is displayed below all the subplot's traces, but above the grid lines.",
+     "description": "Sets the layer on which this zeroline is displayed. If *above traces*, this zeroline is displayed above all the subplot's traces If *below traces*, this zeroline is displayed below all the subplot's traces, but above the grid lines. Limitation: *zerolinelayer* currently has no effect if the *zorder* property is set on any trace.",
      "dflt": "below traces",
      "editType": "plot",
      "valType": "enumerated",
@@ -16204,7 +16204,7 @@
      "valType": "color"
     },
     "zerolinelayer": {
-     "description": "Sets the layer on which this zeroline is displayed. If *above traces*, this zeroline is displayed above all the subplot's traces If *below traces*, this zeroline is displayed below all the subplot's traces, but above the grid lines.",
+     "description": "Sets the layer on which this zeroline is displayed. If *above traces*, this zeroline is displayed above all the subplot's traces If *below traces*, this zeroline is displayed below all the subplot's traces, but above the grid lines. Limitation: *zerolinelayer* currently has no effect if the *zorder* property is set on any trace.",
      "dflt": "below traces",
      "editType": "plot",
      "valType": "enumerated",