[CSSWG][css-values-4] Updated WD of CSS Values and Units Level 4

The CSS WG has published an updated Working Draft of the CSS Values and Units 
Module Level 4:
     http://www.w3.org/TR/css-values-4/

This specification defines the CSS property definition grammar, and
the value types that are common across many specs, such as <length> or
<string>.

New to this draft are the large, small, and dynamic viewport units (lv*, sv*, 
dv*) which allow authors to more precisely size things in relation to the 
dynamically retracting UI of mobile Web browsers. See
   http://www.w3.org/TR/css-values-4/#viewport-relative-lengths

Significant changes since the last WD are all listed at:
   https://www.w3.org/TR/2021/WD-css-values-4-20210715/#changes

Please review the draft, and send any comments to this mailing list,
<www-style@w3.org>, prefixed with [css-values-4] (as I did on this
message) or (preferably) file them in the GitHub repository at
https://github.com/w3c/csswg-drafts/issues

For the CSS WG,
~fantasai