Update README.md

Repo rename; update links

README.md

@@ -5,7 +5,7 @@ the second edition of which was jointly published in 2003 by W3C as a W3C Recomm
 and by ISO as an International Standard ISO/IEC 15948:2003 (E)
 with identical contents.
 
-This repository is being used to work on an [Editors Draft](https://w3c.github.io/PNG-spec/),
+This repository is being used to work on an [Editors Draft](https://w3c.github.io/png/),
 and also for discussion and update of technical changes or additions.
 
 A First Public Working Draft of the [Third Edition of PNG](https://www.w3.org/TR/2022/WD-png-3-20221025/) 
@@ -15,7 +15,7 @@ and [updated](https://www.w3.org/TR/2023/WD-png-3-20230720/) on 20 July 2023
 
 PNG Third Edition became a [Candidate Recommendation](https://www.w3.org/TR/2023/CR-png-3-20230921/) on 21 September 2023 ([Changes since previous publication](https://www.w3.org/TR/2023/CR-png-3-20230921/#changes-20230720))
 
-There is an [Explainer](https://github.com/w3c/PNG-spec/blob/main/Third_Edition_Explainer.md) for features new in the Third Edition,
-and an [Implementation Report](https://w3c.github.io/PNG-spec/Implementation_Report_3e/).
+There is an [Explainer](https://github.com/w3c/png/blob/main/Third_Edition_Explainer.md) for features new in the Third Edition,
+and an [Implementation Report](https://w3c.github.io/png/Implementation_Report_3e/).
 
-The [PNG Extensions specification](https://w3c.github.io/PNG-spec/extensions/Overview.html) is also here.
+The [PNG Extensions specification](https://w3c.github.io/png/extensions/Overview.html) is also here.