Suggestion: add no-banner flag

[ls-gs]

Sometimes it is necessary to set banner: true in config.yaml while still override them occasionally with flags. However currently it's impossible to do so.

From common argparse practise these boolean flags are provided in pairs: --banner and --no-banner, so that the boolean flags can have a chance to override configs no matter which state was set before.

Will Kemono Scraper consider to add this support? Thank you.