feat: add extra={'stack': True} support for logbook handler

[shidenggui]

In logging handler, we can use extra={'stack': True} argument on log method to capture a stack trace, but that argument misses in logbook handler.

# If you don't have an exception, but still want to capture a
# stacktrace, use the `stack` arg
logger.error('There was an error, with a stacktrace!', extra={
    'stack': True,
})