**Description**

Enabled list of cors headers origin allowed

**Use case / motivation**

I'm currently developping Django application working with apache airflow for some external work through api. From Django, user run dag and a js request wait for dag end. By this way, I enabled cors headers in airflow.cfg with correct url. But now, I've  environment (dev & prod). It could be useful to be able to set more than one url in airflow.cfg cors header origin allowed

Thank's in advance :) 

airflow/configuration.py
}
    
    
    deprecated_values = {
        'core': {
            'hostname_callable': (re.compile(r':'), r'.', '2.1'),
        },
        'webserver': {
            'navbar_color': (re.compile(r'\A#007A87\Z', re.IGNORECASE), '#fff', '2.1'),
        },
        'email': {
            'email_backend': (
                re.compile(r'^airflow\.contrib\.utils\.sendgrid\.send_email$'),
                r'airflow.providers.sendgrid.utils.emailer.send_email',
                '2.1',
            ),
        },
    }
    
    
    
    def optionxform(self, optionstr: str) -> str:
        return optionstr
    def __init__(self, default_config=None, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.airflow_defaults = ConfigParser(*args, **kwargs)
        if default_config is not None:
            self.airflow_defaults.read_string(default_config)
        self.is_validated = False
    def validate(self):