[gsoc22] display number of clients

[mwarning]

Meshviewer allows to display the number of clients connected as small circles. Some mods show the number of 2.4 and 5GHz clients as different colored circles.

Is there a way to add this feature without having to modify netjsongraph.js? Maybe support some hook into netjsongraph.js for doing this? Maybe this is already possible?

Here is some code: https://github.com/mwarning/MeshGraphViewer/blob/master/www/utils.js#L6