[css-align-3] Update Changes list

Author: fantasai

css-align-3/Overview.bs

@@ -9,6 +9,8 @@ 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/2020/WD-css-align-3-20200421/
+Previous Version: https://www.w3.org/TR/2018/WD-css-align-3-20181206/
 Previous Version: https://www.w3.org/TR/2018/WD-css-align-3-20180830/
 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/
@@ -2356,6 +2358,15 @@ Appendix A: Static Position Terminology</h2>
 <h2 id="changes">
 Changes</h2>
 
+	Changes since the <a href="https://www.w3.org/TR/2018/WD-css-align-3-20181206/">6 December 2018 Working Draft</a> include:
+	<ul>
+		<li>Improved the center self-alignment of absolutely-positioned elements.
+		<a href="https://github.com/w3c/csswg-drafts/issues/4659">Issue 4659</a>
+		<li>Fixed inconsistent fallback of baseline alignment in mixed writing modes.
+		<a href="https://github.com/w3c/csswg-drafts/issues/3454">Issue 3454</a>
+		<li>Minor editorial fixes and clarifications.
+	</ul>
+
 	Changes since the <a href="https://www.w3.org/TR/2018/WD-css-align-3-20180830/">30 August 2018 Working Draft</a> consist of some minor clarifications.
 
 	Changes since the <a href="https://www.w3.org/TR/2018/WD-css-align-3-20180423/">23 April 2018 Working Draft</a> include: