Feature proposal: Additional custom SnapList

[beig]

Hi,

I want to combine https://github.com/manubb/Leaflet.PixiOverlay with Geoman without losing the functionality of snapping to marker.
My current take on it would be to expose an Array in L.PM.Utils and combining it with the created SnapList in the Snapping._createSnapList function (and also in other places where the SnapMixin is used)

This would give the user a SnapList which he himself can populate/update without changing much of the Snapping function.

Would love to hear your thoughts on this approach.
If it's something you think is useful I would gladly provide a pull request.

Thanks

[Falke-Design]

The easiest would be to create for each coordinate an invisible marker: L.marker(latlng, {opacity: 0, snapIgnore: false, pmIgnore: true}).addTo(map) But maybe that are then to much markers.

Another approche would be to add the markers to _otherSnapLayers for each layer / draw-pm instance.

[beig]

Another advantage would be that the second snaplist can be updated with whats in the viewport.
Having lots of markers in the SnapList makes the mouse pretty laggy