Update README.md (#4421)

README.md

@@ -9,6 +9,8 @@ This repository is the canonical source for REST API specifications for Microsof
 ## Basics
 If you're a spec author looking for information about all of of the repositories and steps in the pipeline, go to the [adx-documentation-pr](https://github.com/Azure/adx-documentation-pr) repository. Make sure to [join the Github Azure organization](http://aka.ms/azuregithub) to get access to that repo. 
 
+<b>Latest improvement:</b><i> MSFT employees can try out our new experience at [OpenAPI Hub](https://aka.ms/openapihub) - online experience for using our validation tools and finding your workflow.</i>
+
 Please check the [announcements page](https://github.com/Azure/azure-rest-api-specs/wiki/Announcements) for any new updates since your last visit.
 
 ## Getting started