Add `AsyncClient`

[afuetterer]

• add asyncclient to _client
• import in init
• set up unasyncd as pre-commit-hook
• _async
• _client (import from _sync and _async), see https://github.com/supabase-community/supabase-py/tree/main/supabase
• add to api reference docs
• add async tests
• update examples in async docstrings
• sort items in __all__
• async log request
• async repository manager
• client: client.event_hooks['request'] = [log_request]
• pytest: asyncio_mode = "auto"

Refs:

• https://pypi.org/project/pytest-asyncio/
• https://www.python-httpx.org/async/
• https://github.com/timofurrer/awesome-asyncio
• https://www.python-httpx.org/advanced/event-hooks/
• https://github.com/python-trio/unasync
• https://github.com/search?q=unasync+path%3Apyproject.toml&type=code
• https://github.com/search?q=unasync+path%3A.github%2Fworkflows&type=code
• https://github.com/search?q=unasync+path%3A.pre-commit-config.yaml&type=code
• https://github.com/search?q=unasyncd+path%3A.pre-commit-config.yaml&type=code
• https://github.com/search?q=tool.unasyncd+path%3Apyproject.toml&type=code