Allow to customize node font color in THEME

[fraxken]

Current theme only allow to update the background color of the Node. However in LIGHT Theme it would be cool to also be able to update the font color for a dark one (for example).

Font color is customizable like the background color:

allNodes[connectedNodes[id]].color = this.colors.CONNECTED;
allNodes[connectedNodes[id]].font.color = "#000";

I guess a restructuration of COLORS constants is necessary:

SELECTED: {
  color: "#673AB7",
  font: {
    color: "#000"
  }
}

I think vis.js allow something like this:

allNodes[connectedNodes[id]].setOptions(this.colors.SELECTED);

[PierreDemailly]

I'm on it