log `extra` param does not work with picologging

[GabrielCappelli]

Passing the extra param on log calls behaves different in picologging compared to stdlib.

Sample code:

import logging
# import picologging as logging

logging.basicConfig(format="message=%(message)s foo=%(foo)s", level=logging.DEBUG)
logging.debug("msg", extra={"foo": "bar"})

Output with std logging: message=msg foo=bar Output with picologging: AttributeError: 'picologging.LogRecord' object has no attribute 'foo'