**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
return _deprecated[name]()
    raise AttributeError(f"module {__name__} has no attribute {name}")
AIRFLOW_HOME = get_airflow_home()
AIRFLOW_CONFIG = get_airflow_config(AIRFLOW_HOME)
_TEST_DAGS_FOLDER = os.path.join(
    os.path.dirname(os.path.dirname(os.path.realpath(__file__))), 'tests', 'dags'
)
if os.path.exists(_TEST_DAGS_FOLDER):
    TEST_DAGS_FOLDER = _TEST_DAGS_FOLDER
else:
    TEST_DAGS_FOLDER = os.path.join(AIRFLOW_HOME, 'dags')
_TEST_PLUGINS_FOLDER = os.path.join(
    os.path.dirname(os.path.dirname(os.path.realpath(__file__))), 'tests', 'plugins'
)
if os.path.exists(_TEST_PLUGINS_FOLDER):
    TEST_PLUGINS_FOLDER = _TEST_PLUGINS_FOLDER
else:
    TEST_PLUGINS_FOLDER = os.path.join(AIRFLOW_HOME, 'plugins')
TEST_CONFIG_FILE = get_airflow_test_config(AIRFLOW_HOME)
SECRET_KEY = b64encode(os.urandom(16)).decode('utf-8')
FERNET_KEY = ''  
WEBSERVER_CONFIG = ''  
conf = initialize_config()
secrets_backend_list = initialize_secrets_backends()
conf.validate()
PY37 = sys.version_info >= (3, 7)
if not PY37:
    from pep562 import Pep562
    Pep562(__name__)