Add a line to the README about the new apache/avro-rs repo for the Ru…

…st SDK

Signed-off-by: Martin Tzvetanov Grigorov <mgrigorov@apache.org>

README.md

@@ -46,6 +46,10 @@ To contribute to Avro, please read:
 
   https://cwiki.apache.org/confluence/display/AVRO/How+To+Contribute
 
+> [!IMPORTANT]  
+> The Rust SDK is moving to https://github.com/apache/avro-rs. Please use it for [new issues](https://github.com/apache/avro-rs/issues/new)
+ and [pull requests](https://github.com/apache/avro-rs/pulls)!
+
 <!-- Arranged this way for easy copy-pasting and editor string manipulation -->
 
 [test c]:          https://github.com/apache/avro/actions/workflows/test-lang-c.yml