[css-grid-3] Update acknowledgements

Author: fantasai

css-grid-3/Overview.bs

@@ -1443,7 +1443,6 @@ Performance Notes</h2>
 	(This performance analysis is from a Gecko perspective,
 	but I suspect there's some truth to it for other layout engines as well.)
 
-
 <h2 id="graceful-degradation">
 Graceful Degradation</h2>
 
@@ -1476,7 +1475,8 @@ Graceful Degradation</h2>
 Acknowledgements</h2>
 
 	Thanks goes to Cameron McCormack who wrote a masonry layout explainer document
-	(from which I lifted the Background chapter) and presented it to the CSSWG.
+	(from which was lifted the Background chapter) and presented it to the CSSWG,
+	and to Mats Palmgren who developed the original version of this specification.
 	Thanks also to everyone who provided feedback on the <a href="https://github.com/w3c/csswg-drafts/issues/4650">initial proposal</a> for this feature.
 
 <h2 id=security>