Update chat prompt in _main function to specify document modification

run.py

@@ -9,7 +9,7 @@ async def _main() -> None:
     async with ChatSession(user="demo_user", session="demo_session") as chat:
         doc_path = chat.upload_document("test.txt")
         print(f"Document uploaded to VM at: {doc_path}")
-        answer = await chat.chat(f"What's in {doc_path}?")
+        answer = await chat.chat(f"Add a line to {doc_path} saying JavaScript sucks!")
         print("\n>>>", answer)