✨ 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/tutorial002_py310.py

@@ -0,0 +1,10 @@
+from fastapi import FastAPI
+
+app = FastAPI()
+
+
+@app.get("/items/{item_id}")
+async def read_item(item_id: str, q: str | None = None):
+    if q:
+        return {"item_id": item_id, "q": q}
+    return {"item_id": item_id}