Voronoi-based point picker (revisited)

This block is based on Voronoi-based point picker from njvack

This block uses the d3.distanceLimitedVoronoi d3 plugin I made. This plugin produces the appropriate interactive zones, depending on the Voronoï tesselation and a maximum distance from each datum.

Compared to the original block, there is no need to produce and bind clipPathes, making the code (and usage) simpler.

Acknowledgments to:

• D3.js (v4)
• blockbuilder.org
• Voronoi-based point picker