[css-text-3] Define interaction of bidi and eol hanging spaces

Closes #4422

Author: frivoal

css-text-3/Overview.bs

@@ -1643,7 +1643,7 @@ Text Processing</h3>
 
       <li>If there remains any sequence of <a>white space</a>,
         and/or [=other space separators=],
-        at the end of a line:
+        at the end of a line (after <a href="https://www.w3.org/TR/css-writing-modes/#text-direction">bidi reordering</a> [[CSS-WRITING-MODES-3]]):
         <ul>
           <li>If 'white-space' is set to ''white-space/normal'', ''white-space/nowrap'', or ''white-space/pre-line'',
             the UA must [=hang=] this sequence (unconditionally).