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

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

docs_src/body/tutorial002_py310.py

@@ -0,0 +1,21 @@
+from fastapi import FastAPI
+from pydantic import BaseModel
+
+
+class Item(BaseModel):
+    name: str
+    description: str | None = None
+    price: float
+    tax: float | None = None
+
+
+app = FastAPI()
+
+
+@app.post("/items/")
+async def create_item(item: Item):
+    item_dict = item.dict()
+    if item.tax:
+        price_with_tax = item.price + item.tax
+        item_dict.update({"price_with_tax": price_with_tax})
+    return item_dict