[css-logical-1] Tweak issue wording

Author: fantasai

css-logical-1/Overview.bs

@@ -131,10 +131,12 @@ Introduction</h2>
   Since implementation of parts of this module is effectively required
   for shipping an implementation of <a href="https://www.w3.org/TR/css-writing-modes-3/">CSS Writing Modes</a> on the Web
   (in order to correctly implement the default HTML styles),
-  The CSSWG resolved that although the draft is not very stable overall,
+  the CSSWG resolved that
   the requisite features in
   <a href="#directional-keywords"></a> and <a href="#box"></a>
   are approved for shipping.
+  (See <a href="https://lists.w3.org/Archives/Public/www-style/2017Dec/0043.html">FPWD announcement</a> for additional background.)
+
   However, there are a few significant open issues:
   <ul>
     <li>The ''border/logical'' keyword on shorthands,