Python: added create_agent and removed need for Field in annotations (#380)

* added create_agent

* add minimal sample

* allow multiple annotations

* improved docstring

python/samples/getting_started/minimal_sample.py

@@ -0,0 +1,21 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+import asyncio
+from random import randint
+from typing import Annotated
+
+from agent_framework.openai import OpenAIChatClient
+
+
+def get_weather(
+    location: Annotated[str, "The location to get the weather for."],
+) -> str:
+    """Get the weather for a given location."""
+    conditions = ["sunny", "cloudy", "rainy", "stormy"]
+    return f"The weather in {location} is {conditions[randint(0, 3)]} with a high of {randint(10, 30)}°C."
+
+
+agent = OpenAIChatClient().create_agent(
+    name="WeatherAgent", instructions="You are a helpful weather agent.", tools=get_weather
+)
+print(asyncio.run(agent.run("What's the weather like in Seattle?")))