[css-display-1] Add changes list.

Author: fantasai

css-display-3/Overview.bs

@@ -1429,6 +1429,20 @@ Acknowledgments</h2>
 <h2 class=no-num id="changes">
 Changes</h2>
 
+	Changes since the <a href="https://www.w3.org/TR/2020/CRD-css-display-3-20201218/">18 December 2020 Candidate Recommendation Draft</a>
+	include:
+
+	<ul>
+		<li id="change-internal-replaced">
+			Defined that [=replaced elements=] with a [=layout-internal=] 'display'
+			are treated as ''display: inline''.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/6000">Issue 6000</a>)
+		<li id="change-block-layout-def">
+			Added definition for [=block layout=] to glossary, for convenience.
+		<li id="change-grid-refs">
+			Updated references to <a href="https://www.w3.org/TR/css-grid/">CSS Grid Layout</a>.
+	</ul>
+
 	Changes since the <a href="https://www.w3.org/TR/2020/CR-css-display-3-20200519/">19 May 2020 Candidate Recommendation</a>
 	consist only of minor editorial clarifications and cross-linking improvements.