✨ Add docs and tests for Python 3.9 and Python 3.10 (#3712)

Co-authored-by: Thomas Grainger <tagrain@gmail.com>

docs_src/query_params/tutorial006b.py

@@ -0,0 +1,13 @@
+from typing import Union
+
+from fastapi import FastAPI
+
+app = FastAPI()
+
+
+@app.get("/items/{item_id}")
+async def read_user_item(
+    item_id: str, needy: str, skip: int = 0, limit: Union[int, None] = None
+):
+    item = {"item_id": item_id, "needy": needy, "skip": skip, "limit": limit}
+    return item