[css-box-3] Update Changes list, metadata.

Author: fantasai

css-box-3/Overview.bs

@@ -7,11 +7,12 @@ Work Status: Refining
 Group: csswg
 ED: https://drafts.csswg.org/css-box-3/
 TR: https://www.w3.org/TR/css-box-3/
-Previous Version: https://www.w3.org/TR/2018/WD-css-box-3-20181218/
+Previous Version: https://www.w3.org/TR/2020/WD-css-box-3-20201028/
 Abstract: This specification describes the margin and padding properties, which create spacing in and around a CSS box.
 Editor: Elika J. Etemad / fantasai, Invited Expert, http://fantasai.inkedblade.net/contact, w3cid 35400
 Ignored Terms: internal table elements, block layout
 At risk: applicability of 'margin', 'padding' and their longhands to [=ruby base containers=] and [=ruby annotation containers=]
+Issue Tracking: CSSWG GitHub https://github.com/w3c/csswg-drafts/issues
 </pre>
 <pre class='link-defaults'>
 spec:css-sizing-3; type:dfn; text:size
@@ -463,11 +464,17 @@ Changes Since CSS Level 2 {#changes}
 	since <a href="https://www.w3.org/TR/CSS2/box.html">CSS Level 2</a>:
 	<ul>
 		<li>Adapting the prose slightly to account for vertical <a>writing modes</a>.
-		<li>Defining the applicability of 'margin', 'padding' and their longhands to [=ruby base containers=] and [=ruby annotation containers=] (at risk)
+		<li>Defining the non-applicability of 'margin', 'padding' and their longhands
+			to [=ruby base containers=] and [=ruby annotation containers=] (at risk).
+		<li>Providing a [[#keywords|centralized common definition]]
+			of keywords that reference the various box edges
+			for use in properties defined outside this spec
+			(e.g. 'background-clip')
+			to avoid repetition (and the resulting inevitable synchronization errors).
 	</ul>
 
 Privacy and Security Considerations {#priv-sec}
 ===============================================
 
-	Box Model introduces no new privacy leaks,
-	or security considerations beyond "implement it correctly".
+	Box Model introduces no new privacy leaks
+	or security considerations.