Update extensions.mdx

Author: aritchie

src/content/docs/release-notes/extensions.mdx

@@ -20,7 +20,7 @@ import RN from '/src/components/ReleaseNote.astro';
 
 ## Extensions
 
-### vNext
+### v1.3.0 - September 16, 2025
 <RN type="enhancement">DI registration now supports `AsSelf` which allows an implementation to be registered directly</RN>
 
 ### 1.2.2 - July 26, 2025