Add snippets for all Layer classes

[hhkaos]

Today the extension contain just a one snippets

Snippet	Description
addLayerFromPortalItem	Add a new layer to the map from an ArcGIS Online or Enterprise portal item. Contains a placeholder for the portal item id.

But there are a lot of (Layer) types.

It would be nice to have snippets for the following classes: (38 in total)

• Vector layers
  • [ ] CSVLayer
  • [ ] GeoJSONLayer
  • [ ] GeoRSSLayer (OGC)
  • [ ] GraphicsLayer
  • [ ] FeatureLayer
  • [ ] FeatureLayer (client-side)
  • [ ] MapNotesLayer
  • [ ] OGCFeatureLayer OGC API - Features
  • [ ] RouteLayer
  • [ ] StreamLayer
  • [ ] VectorTileLayer
  • [ ] WFSLayer OGC Web Feature Service (WFS)
• Raster Layers
  • [ ] ImageryTileLayer
  • [ ] ImageryLayer
  • [ ] ImageryTileLayer /w COG
  • [ ] ImageryTileLayer (Multidimensional)
  • [ ] WebTileLayer - (XYZ layer / Slippy maps)
  • [ ] WMSLayer OGC Web Map Service (WMS)
  • [ ] WMTSLayer OGC Web Map Tile Service (WMTS)
  • [ ] WCSLayer OGC Web Coverage Service (WCS)
  • [ ] MapImageLayer (Time-based) Traffic layer
  • [ ] BingMapsLayer
  • [ ] OpenStreetMapLayer
• 3D layers
  • [ ] SceneLayer
  • [ ] Elevation
  • [ ] PointCloud
  • [ ] BuildingSceneLayer
  • [ ] LineOfSightLayer
  • [ ] DimensionLayer
  • [ ] IntegratedMeshLayer
  • [ ] VoxelLayer
• Others
  • [ ] MediaLayers (Overlayed images with control points)
  • [ ] MediaLayers (/w video)
  • [ ] KML Layer (OGC)
  • [ ] GroupLayer
  • [ ] SubtypeGroupLayer
  • [ ] TileLayer
  • [ ] KnowledgeGraphLayer

Most of these layers have the possibility to be initialized in different ways (e.g. using source or a similar property), with a url, and/or using a portalItem. Like FeatureLayer (using: source, url, portalItem), RouteLayer (using: stops, url and portalItem, StreamLayer (webSocketUrl or url), etc.

I think the portalItem is the easiest to remember, and having addLayerFromPortalItem I don't see that very relevant. I also think using the URL is probably one of the most commons ways, but also the easiest to remember. I would say having the custom-source/client-side (for been the most complex to remember) or both (including url) if you think that should be default, would be my preference for these snippets.

Does it make sense @kellyhutchins ? // cc: @RalucaNicola