[CSSWG][css-text-3] Updated WD of CSS Text L3

The CSS WG has published an updated Working Draft of the CSS Text Module Level 3:
     https://www.w3.org/TR/css-text-3/

This module contains various typesetting properties not related to font
selection, such as alignment, line breaking, white space collapsing,
text justification, and other forms of text-level spacing adjustments.

Most changes since the November 2019 draft are minor fixes. However there is 
one major change to the segment break transformation rules: they have been 
redrafted against an explicit list of Unicode code blocks rather than a set of 
property intersection rules based off of the East Asian Width property.

This is change is for two reasons: 1. Unicode modified EAW in a 
backwards-incompatible way, yielding much weirder results for this operation 
than previously and 2. based on implementation feedback, we needed a much 
simpler rule that would be fast to implement since this operation is hot. The 
WD now contains an initial draft of the new approach, see:
   https://www.w3.org/TR/css-text-3/#line-break-transform
and
   https://www.w3.org/TR/css-text-3/#space-discard-set

Please review the draft, and send any comments to the CSSWG mailing list,
<[email protected]>, prefixed with [css-text-3] (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