add example for the researcher role

examples/research.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python
+
+import asyncio
+
+from metagpt.roles.researcher import RESEARCH_PATH, Researcher
+
+
+async def main():
+    topic = "dataiku .vs datarobot"
+    role = Researcher(language="en-us")
+    await role.run(topic)
+    print(f"save report to {RESEARCH_PATH / f'{topic}.md'}.")
+
+
+if __name__ == '__main__':
+    asyncio.run(main())