[css-align-3] Update Changes section

Author: fantasai

css-align-3/Overview.bs

@@ -9,6 +9,7 @@ ED: https://drafts.csswg.org/css-align/
 TR: https://www.w3.org/TR/css-align-3/
 Editor: Elika J. Etemad / fantasai, Invited Expert, http://fantasai.inkedblade.net/contact, w3cid 35400
 Editor: Tab Atkins Jr., Google, http://xanthir.com/contact/, w3cid 42199
+Previous Version: https://www.w3.org/TR/2018/WD-css-align-3-20180423/
 Previous Version: https://www.w3.org/TR/2017/WD-css-align-3-20170906/
 Previous Version: https://www.w3.org/TR/2017/WD-css-align-3-20170720/
 Previous Version: https://www.w3.org/TR/2017/WD-css-align-3-20170515/
@@ -2281,7 +2282,18 @@ Appendix A: Static Position Terminology</h2>
 <h2 id="changes">
 Changes</h2>
 
-	Changes since the <a href="https://www.w3.org/TR/2017/WD-css-align-3-20170720/#changes">6 September 2017 Working Draft</a> include:
+	Changes since the <a href="https://www.w3.org/TR/2018/WD-css-align-3-20180423/">23 April 2018 Working Draft</a> include:
+	<ul>
+		<li>Better definition of how the alignment properties interact with absolutely-positioned boxes with ''left/auto'' offsets.
+		See [[#justify-abspos]], [[#align-abspos]], [[#abspos-sizing]], and [[#staticpos-rect]].
+		<li>More detailed definition of how <a>content-alignment</a> works on <a>scroll containers</a>.
+		See [[#overflow-scroll-position]].
+		<li>Noted CSS2’s special rules about the baselines of inline-block <a>scroll containers</a>.
+		<li>Defined that percentage gaps compute against zero when calculating intrinsic sizes, and resolve during layout. (<a href="https://github.com/w3c/csswg-drafts/issues/509">Issue 509</a>)
+		<li>Miscellaneous minor clarifications.
+	</ul>
+
+	Changes since the <a href="https://www.w3.org/TR/2017/WD-css-align-3-20170906/">6 September 2017 Working Draft</a> include:
 	<ul>
 		<li>Added more illustrations! Many thanks to Melanie Richards for working through a difficult diagramming problem.
 		<li>Fixed errors in property definition table of 'gap' shorthand.