[css-highlight] Update Changes section

Author: frivoal

css-highlight-api-1/Overview.bs

@@ -618,7 +618,39 @@ Appendix C. Changes</h2>
 
 	<em>This section is non-normative</em>.
 
-	There have been only editorial changes since the previous <a href="https://www.w3.org/TR/2020/WD-css-highlight-api-1-20201022/">Working Draft</a>;
+<h3 class=no-num" id="changes-since-20201208">
+Changes since the <a href="https://www.w3.org/TR/2020/WD-css-highlight-api-1-20201208/">8 December 2020 Working Draft</a></h3>
+
+	In addition to various editorial improvements and minor tweaks,
+	the main changes are:
+
+	* Renamed <code>HighlightsRegister</code> to {{HighlightRegistry}}
+	* Removed the redundant <code>add()</code> method from {{HighlightRegistry}}.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/6092">Issue 6092</a>)
+	* Make custom highlight overlays stack below native highlight overlays.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/4595">Issue 4595</a>)
+	* Handle highlight priority with integers rather than floats.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/4592">Issue 4592</a>)
+	* Define the default value for highlight priority to be 0.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/6136">Issue 6136</a>)
+	* Made HighlightRegistry maplike (rather than setlike)
+		and remove <code>name</code> property from Highlight.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/5910">Issue 5910</a>)
+	* Clarified that ranges from the wrong window are not painted.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/6417">Issue 6417</a>)
+	* Specify that custom highlights have no UA styles.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/6375">Issue 6375</a>)
+	* Deferred to the [[DOM]] specification for range invalidation
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/4597">Issue 4597</a>)
+	* Added a {{Highlight/type}} attribute to {{Highlight}}
+		to give clearer semantics to different highlights,
+		in support of exposing highlights to accessibility tools.
+		(See <a href="https://github.com/w3c/csswg-drafts/pull/6498">Issue 6498</a>)
+
+<h3 class=no-num" id="changes-since-20201022">
+Changes since the <a href="https://www.w3.org/TR/2020/WD-css-highlight-api-1-20201022/">22 October 2020 Working Draft</a></h3>
+
+	There have been only editorial changes since the <a href="https://www.w3.org/TR/2020/WD-css-highlight-api-1-20201022/">22 October 2020 Working Draft</a>;
 	see <a href="https://services.w3.org/htmldiff?doc1=https%3A%2F%2Fwww.w3.org%2FTR%2F2020%2FWD-css-highlight-api-1-20201022%2F&doc2=https%3A%2F%2Fwww.w3.org%2FTR%2Fcss-highlight-api-1%2F">diffs</a>.
 </div>