Update README.md for Sematic Router Example (microsoft#3846)

Added contributors to recognize the other devs who helped build the example

Co-authored-by: Eric Zhu <[email protected]>

Author: tarockey

python/packages/autogen-core/samples/semantic_router/README.md

@@ -75,3 +75,8 @@ sequenceDiagram
     User_Proxy_Agent->>Closure_Agent: Confirm session end
     Closure_Agent->>User: Display session end message
 ```
+### Contributors
+
+- Diana Iftimie (@diftimieMSFT)
+- Oscar Fimbres (@ofimbres)
+- Taylor Rockey (@tarockey)