Highlight map points from the same structure

[Luthaf]

When in atom mode, it would be good to highlight on the map other points pertaining to the same structure as the currently selected atom.

A good way to do that would be to dim / grey out other points, using the same mechanism as #3.

[ceriottm]

I think this could/should go hand-in-hand with the highlighting of the "clickable" atoms in the JSMolWidget. When in environment mode, one should see all the environments highlighted in the JSMolWidget, and the corresponding points should be highlighted in the scatter plot - perhaps just made 2x larger, with thicker outline, and brought to front in the z-index.

[Luthaf]

and brought to front in the z-index.

This is not easy since we are not using HTML to render the graph but WebGL (which is why we are able to render more than 10k points 😄). Instead we would need the same kind of bookeeping infrastructure as for #16 for coloring.

Bringing points on front would require either using a second plotly trace, with the related performance issue when changing the selected point --- this is why we use a small hack to display selected point in 2D mode --- or duplicating the same hack for all highlighted points.