Add layer toggle widget

[weca-theo]

I often build Crowdsource Reporter apps which show a couple of different map layers to the user. However, I want to give the user the ability to turn off/on map layers if required. For example, to clear up the map or to focus on only 1 layer. There is no current option in the app configure view to add this toggle. This functionality is fairly basic, so I hope it'd an easy enhancement.

Currently we only get these options:

I also noticed it doesn't appear on other apps (Survey 123, GeoForm etc.).

[weca-theo]

Duplicate of #495