Angular: Document `window.ng`, ng.coreTokens, and ng.probe()

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Performance issue
[ ] Feature request
[x] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question
[ ] Other... Please describe:

Current behavior

window.ng is not documented and contains a few items.

ng.probe() some sort of component debugging?
ng.coreTokens contains appref, router, etc but they are just the classes instead of instances? Does this work with ng.probe somehow?

It is used for some debugging purposes and referenced by the augury docs.

https://augury.rangle.io/pages/guides/architecture.html

Environment

Angular version: 7.0.0