Add documentation for classes.ts

[diegobfernandez]

I see in some places you guys use classes.ts however there is no documentation on the site for it.
I think it is great and can be very useful sometimes.
My suggestion is to add the appropriate constants in each components doc page for easy reference.

[giladgray]

I can't think of a good / clean way to list the Classes constants for a component on its docs page. That feels like more noise than signal. However, simply mentioning Classes somewhere in the docs as a place where you can find all the CSS constants should be easy enough!

[giladgray]

oh hey this was done in #2325