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

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

docs_src/schema_extra_example/tutorial002_py310.py

@@ -0,0 +1,17 @@
+from fastapi import FastAPI
+from pydantic import BaseModel, Field
+
+app = FastAPI()
+
+
+class Item(BaseModel):
+    name: str = Field(..., example="Foo")
+    description: str | None = Field(None, example="A very nice Item")
+    price: float = Field(..., example=35.4)
+    tax: float | None = Field(None, example=3.2)
+
+
+@app.put("/items/{item_id}")
+async def update_item(item_id: int, item: Item):
+    results = {"item_id": item_id, "item": item}
+    return results