document mouseenter/mouseleave

[peterqliu]

As used in the hover popup example.

Looks like these are different from the other mouse events, as they pertain to specific style layers, rather than the map object as a whole.

[mollymerp]

Oh good catch – it's only mentioned here https://www.mapbox.com/mapbox-gl-js/api/#map#on

If you want to add it it would go at the bottom of src/ui/map.js with the other map events https://github.com/mapbox/mapbox-gl-js/blob/master/src/ui/map.js#L1718-L1760 😸

[jfirebaugh]

Added in #5126.