adds small blurb to index on new release

index.md

@@ -16,6 +16,8 @@ Just the Docs gives your documentation a jumpstart with a responsive Jekyll them
 
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+**New: version `0.4.0.rc1` has just been released! See [the changelog](https://github.com/just-the-docs/just-the-docs/blob/main/CHANGELOG.md) for a detailed breakdown!**
+
 ## Getting started
 
 ### Dependencies