Support per node styling

[GiantRobato]

Is your feature request related to a problem? Please describe. A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

I'm using dependentree to visualize dependencies but sometimes a dependency fails. It would be helpful for me to color those dependencies separately from the other nodes.

Describe the solution you'd like Add in the constructor a way to specify a field to look for if you want to override the default node color. Example:

// js
const tree = new DependenTree("div#tree", {
      overrideColorField : "_color"
    });


// json
[
    {
        "_name": "Component",
        "_deps": [
            "Extension 1",
            "Extension 2"
        ],
       "_color": "red"
    }
]

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Add any other context or screenshots about the feature request here.