docs(cdk/layout): better explain how layout breakpoints work (#22821)
docs(cdk/layout): better explain how layout breakpoints work (#22821)

I'm copying the actual breakpoints here for reference because it's much
easier to parse than looking at the archived Material Design site.

I'm also working on a follow-up to add an overview example for
`BreakpointObserver`.

Fixes #11788
mmalerba/material2,DevVersion/material2,josephperrott/material2,angular/components,josephperrott/material2,DevVersion/material2,angular/components,josephperrott/material2,josephperrott/material2,crisbeto/material2,crisbeto/material2,josephperrott/material2,mmalerba/material2,DevVersion/material2,DevVersion/material2,crisbeto/material2,crisbeto/material2,mmalerba/material2,angular/components,mmalerba/material2,angular/components,mmalerba/material2,DevVersion/material2