is there any documentation or example for forge viewer to integrate the point cloud visualisation lib Potree with Forge viewer?
Here's an experimental branch of potree-core that's been back-ported to three.js v71 (the one used by Forge Viewer): https://github.com/petrbroz/potree-core/tree/experiment/three71.
And here's a demo of the potree loader used in Forge Viewer: https://github.com/petrbroz/forge-potree-demo.