Support .toml configuration format with --config flag

[bricker]

Fixes #193

Adds support for a TOML-formatted configuration file when using the --config command line argument.

Currently, passing a TOML file into the --config argument results in this error:

autoflake --config ./path/to/pyproject.toml test_me.py

#  File "[...]/.local/share/pyenv/versions/3.11.2/lib/python3.11/configparser.py", line 1132, in _read
#    raise e
# configparser.ParsingError: Source contains parsing errors: PosixPath('./path/to/pyproject.toml')

[fsouza]

Thank you!