Proposal for css Selectors Level 4

Good afternoon, I apologize for my poor English ..
I want to offer to contribute to css Selectors Level 4
Vertical centering, text, blocks
eg "margin: auto 0",  "margin: auto auto"
Horizontal alignment is well thought out and convenient! You need to think
about it, vertical centering! That it was so convenient ..
Thanks..











My contacts
https://github.com/brendan8c