docs: add missing microsoft-agents-hosting-fastapi to Packages Overview

[Copilot]

Summary

The microsoft-agents-hosting-fastapi package exists in the libraries/ directory and is published on PyPI, but was missing from the Packages Overview table in README.md.

Changes

• Added microsoft-agents-hosting-fastapi row to the Packages Overview table with a PyPI version badge, description, and "Replaces" column entry
• Added a FastAPI import example to the Import Examples section alongside the existing aiohttp example

[Copilot]

Pull request overview

Updates the repository’s top-level documentation to reflect that the FastAPI hosting package is part of the SDK and to show how to import it, aligning the README with the packages actually present/published.

Changes:

• Added a FastAPI import example in the “Import Examples” section.
• Added microsoft-agents-hosting-fastapi to the “Packages Overview” table with a PyPI badge and description.

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[Copilot]

In the single Import Examples code block, both aiohttp and FastAPI imports bind the same name start_agent_process. If a user copies the whole block, the FastAPI import will overwrite the aiohttp import, which is confusing and can lead to using the wrong framework helper. Consider splitting these into separate code blocks, or aliasing the imports (e.g., start_agent_process as aiohttp_start_agent_process / ... as fastapi_start_agent_process) to make the example copy/paste-safe.

Suggested change

	from microsoft_agents.hosting.aiohttp import start_agent_process
	# FastAPI hosting
	from microsoft_agents.hosting.fastapi import start_agent_process
	from microsoft_agents.hosting.aiohttp import start_agent_process as aiohttp_start_agent_process
	# FastAPI hosting
	from microsoft_agents.hosting.fastapi import start_agent_process as fastapi_start_agent_process