[css-display-3] Update Changes list

Author: fantasai

css-display-3/Overview.bs

@@ -1257,8 +1257,10 @@ Changes</h2>
 		(which is definitely not “as specified”, due to <a>blockification</a> and <a>inlinification</a> rules triggered by various properties).
 		(<a href="https://github.com/w3c/csswg-drafts/issues/1716">Issue 1716</a>)
 	* Added definition for <a>document order</a>.
-	* Added missing SVG elements to <a hrerf="#unbox">Appendix B</a>’s details on ''display: contents''.
+	* Added missing SVG elements to <a hrerf="#unbox">Appendix B</a>’s details on ''display: contents''
 		(<a href="https://github.com/w3c/csswg-drafts/issues/2118">Issue 2118</a>)
+		and defined behavior for MathML
+		(<a href="https://github.com/w3c/csswg-drafts/issues/2167">Issue 2167</a>).
 	* Added some <a href="#box-guidance">guidance</a> to future spec authors of anonymous box construction rules.
 		(<a href="https://github.com/w3c/csswg-drafts/issues/1643">Issue 1643</a>)
 	* Pushed the section about “becoming a formatting context” back to <a href="https://www.w3.org/TR/css-contain-1/">CSS Containment</a> where it is used.