Add basic snippets

[hhkaos]

In addition to the existing snippets, which I would recommend revisiting to make them clearer (like with map)

It would be nice adding some additional ones:

• [x] require
• Map:
  • [x] create2DMap (a.k.a map)
  • [x] create3DScene (a.k.a. scene)
  • [x] load2DWebmap (a.k.a webmap)
  • [x] load3DScene (a.k.a. webscene)
• View:
  • [ ] hitTest
  • [ ] mapViewConstraints: scale, zoom, rotation, extent
  • [ ] sceneViewConstraints: for camera tilt and altitude
• Markers:
  • [ ] addDefaultMarkerToView
  • [ ] addCustomMarkerToView
  • [ ] addMarkerWithPopup
• Navigation:
  • [ ] enableSmoothScrollNavigation snapToZoom
  • [ ] disableViewNavigation
  • [ ] disableViewRotation
  • [ ] disableViewMouseWheelNavigation
  • [ ] disableViewSingleTouchNavigation
• Others
  • [ ] watchPropertyChanges (reactiveUtils)
  • [ ] watchPropertyChanges (Accessor.watch())