Make `pointer-events` configurable

[janfabry]

We set the pointer-events manually to auto (since #22, modified in #75), but it would be nice if the value would be configurable.

Example use case: I would like to set them to visible instead of auto, to be able to get mouse events for features without a fill.

[wlievens]

I would like this too, for the opposite case: making a layer "click-through" so that clicks are triggered on the layers below.

[wlievens]

Actually it seems the interactive option covers this for my use case.