[change] Show node labels only after hitting a certain zoom level

[totallynotvaishnav]

Currently, when we zoom out too much the labels of the nodes look cluttered and they are unreadable. We should allow the library to configure the level of zoom at which we want to start seeing node labels.

[nemesifier]

I am reopening this because I found out how to do this:

graph.echarts.on('graphRoam', function(e) {
  console.log(graph.echarts.getOption().series[0].zoom);
});