📝 Add documentation of example kwarg of Field (#1106)

* Add documentation of example kwarg of Field

* 📝 Update info about schema examples

* 🚚 Move example file to new directory

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

docs_src/body_fields/tutorial003.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 = Field(None, example="A very nice Item")
+    price: float = Field(..., example=35.4)
+    tax: float = 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