[css-align-3] Update Changes list

Author: fantasai

css-align-3/Overview.bs

@@ -2168,6 +2168,22 @@ Aligning Boxes by Baseline</h3>
 <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:
+	<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.
+		<li>Defining percentage gaps to resolve to zero when the containing block’s size depends on the gaps.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/509">Issue 509</a>,
+		<a href="https://github.com/w3c/csswg-drafts/issues/2297">Issue 2297</a>)
+		<li>Fixed errors in handling <css>left</css> and <css>right</css> in the grammars.
+		<li>Fixed discrepency in ''align-content/space-align'' fallback alignment.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/2316">Issue 2316</a>)
+		<li>Tightened up handling of baseline alignment in cases where the box edges don't align.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/1556">Issue 1556</a>,
+		<a href="https://github.com/w3c/csswg-drafts/issues/1611">Issue 1611</a>)
+		<li>Miscellaneous clarifications.
+	</ul>
+
 	Changes since the <a href="https://www.w3.org/TR/2017/WD-css-align-3-20170720/#changes">20 July 2017 Working Draft</a> include:
 	<ul>
 		<li>Added the 'row-gap' and 'column-gap' properties and 'gap' shorthand,