Some questions about the use of Typography

[gkj17]

Description

I found that in Typography.md there seems to be nothing about how to use headline3 or headline4 or ..... subTitle1 subTitle2 as such? So please tell me how I should use it now?

[asyncLiz]

Material's applying type guidelines has explanations on the purpose of each typescale role and where to use them.

I created #5553 to add that info to our typography docs!