[css-position-3] Update Changes list

Author: fantasai

css-position-3/Overview.bs

@@ -1721,6 +1721,9 @@ Acknowledgments</h2>
 	The following significant changes were made since the
 	<a href="https://www.w3.org/TR/2022/WD-css-position-3-20220901/">01 September 2022 Working Draft</a>:
 	<ul>
+		<li>Added [[#stacking]] and defined [=sticky-positioned boxes=]
+			to always form a [=stacking context=].
+			(<a href="https://github.com/w3c/csswg-drafts/issues/1053">Issue 1053</a>)
 		<li>Updated [=sticky positioning=] to using its offsetted positioning
 			for scroll operations.
 			(<a href="https://github.com/w3c/csswg-drafts/issues/7930">Issue 7930</a>)