Add optional dependency for PySocks to support proxy

[Klork-droid]

Summary

The aiomqtt library depends on paho-mqtt, which has an optional dependency on PySocks for proxy support. Currently, aiomqtt does not include this optional dependency, making it difficult for users to leverage proxy functionality with aiomqtt without adding PySocks manually to requirements for their project.

Proposed Change

Add the optional dependency PySocks to the pyproject.toml of aiomqtt in [project.optional-dependencies] to align with the optional dependencies of paho-mqtt.

Details

The paho-mqtt library includes the following optional dependency in its pyproject.toml:

[project.optional-dependencies]
proxy = [
    "PySocks",
]