Fully define dependencies for async support via optional dependency group

The current docs suggest adding aiohttp as a dependency to create an async app, but this creates a direct dependency on aiohttp for consumers of slack-bolt on what is is really a transitive dependency for the consumer of slack-bolt. This is especially important because this leaves it to consumers to find compatible versions of slack-bolt and aiohttp without the aide of a package manager.

slack-bolt should define an optional dependency group and include aiohttp so that consumers of this library don't need to maintain a dependency on a transitive. Consumers would be able to uv add slack-bolt[async] for example to include the optional dependencies.

Category (place an x in each of the [ ])

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• [] Others

Requirements

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Start with the documentation for slack_bolt.async_app.AsyncApp and the package metadata that defines dependencies. Check how async support is currently installed, then verify that the optional async dependency group includes aiohttp and that the documented uv add slack-bolt[async] workflow installs it without requiring consumers to manage it directly.