add ColormakerRegistry?

[hainm]

Not sure it it's useful in nglview. Or may be just let people do that in ngl?

[hainm]

https://github.com/arose/ngl/blob/master/doc/usage/coloring.md#selection-based-coloring

var schemeId = NGL.ColormakerRegistry.addSelectionScheme([
  ["red", "64-74 or 134-154 or 222-254 or 310-310 or 322-326"],
  ["green", "311-322"],
  ["yellow", "40-63 or 75-95 or 112-133 or 155-173 or 202-221 or 255-277 or 289-309"],
  ["blue", "1-39 or 96-112 or 174-201 or 278-288"],
  ["white", "*"]
], "Transmembrane 3dqb");

stage.loadFile("rcsb://3dqb.pdb").then(function (o) {
  o.addRepresentation("cartoon", {color: schemeId });  // pass schemeId here
  o.autoView();
});

[hainm]

[hainm]

done in master.