Support valueExpression property of renderer.

[paulamaddock]

The plugin does not support the valueExpression property in rendering.

{
  "renderer": {
    "authoringInfo": {
      "type": "classedSize"
    },
    "type": "classBreaks",
    "field": null,
    "valueExpression": "var days_since_treatment = DateDiff(Today(),$feature[\"LAST_EDIT_DATE_COPY\"],'days')\nreturn Round(days_since_treatment)",
    "valueExpressionTitle": "Custom",
    "defaultSymbol": {
      "color": [
        255,
        255,
        255,
        255
      ],
      "width": 1.5,
      "type": "esriSLS",
      "style": "esriSLSSolid"
    },
    "minValue": 0,
    "classBreakInfos": [ ],
    "defaultLabel": "Not treated yet"
  },
  "transparency": 0
}

[jgravois]

more info in ynunokawa/L.esri.WebMap#74

[jwasilgeo]

and more related info in Esri/esri-leaflet#1195