chore: adds move notice to README.md (#608)

Author: claymcleod

README.md

@@ -31,6 +31,11 @@
   </p>
 </p>
 
+## ⚠️ REPOSITORY WARNING
+
+> **These crates have moved to the [`stjude/sprocket`](https://github.com/stjude-rust-labs/sprocket) repository under the [`crates`](https://github.com/stjude-rust-labs/sprocket/tree/main/crates) directory.**
+> Please direct all future development, discusssions, and issues there. Thank you!
+
 ## 📚 Getting Started
 
 The `wdl` family of crates consists of (a) a number of component crates (any