Description
Raster functions are operations performed on a raster to apply on-the-fly processing. This sample demonstrates how to create an image service raster and apply a Hillshade raster function to it.

How it works
- Create AGSImageServiceRaster using a URL and load it.
- Create AGSRasterFunction using a JSON string.
- Get raster function's arguments with rasterFunction.arguments.
- Set image service raster in the raster function arguments with name using setRaster(_ raster: AGSRaster, withName name: String).
- Create AGSRaster using AGSRasterFunction.
- Create AGSRasterLayer using AGSRaster.
- Add AGSRasterLayer to AGSMap.operationalLayers array.