Investigate solution for glTF-Assets-Viewer when referrer-policy is more strict

[bghgary]

The way assets are being view using the view link in the readmes in the output folder will no longer work in future versions of browsers where security will be tighter. We need to investigate a different way to do this.

https://github.com/bghgary/glTF-Assets-Viewer/blob/master/index.js#L241

document.referrer will no longer return the whole address of the referrer.

See https://codereview.chromium.org/684683003/ for some context.