**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/www/extensions/init_views.py
"""Init main app view - redirect to FAB"""
    from airflow.www.blueprints import routes
    app.register_blueprint(routes)
def init_appbuilder_views(app):
    """Initialize Web UI views"""
    appbuilder = app.appbuilder
    from airflow.www import views
    
    
    appbuilder.session.remove()
    appbuilder.add_view_no_menu(views.DagModelView())
    appbuilder.add_view_no_menu(views.Airflow())
    appbuilder.add_view(
        views.DagRunModelView,
        permissions.RESOURCE_DAG_RUN,
        category=permissions.RESOURCE_BROWSE_MENU,
        category_icon="fa-globe",
    )
    appbuilder.add_view(
        views.JobModelView, permissions.RESOURCE_JOB, category=permissions.RESOURCE_BROWSE_MENU
    )
    appbuilder.add_view(
        views.LogModelView, permissions.RESOURCE_AUDIT_LOG, category=permissions.RESOURCE_BROWSE_MENU
    )
    appbuilder.add_view(
        views.VariableModelView, permissions.RESOURCE_VARIABLE, category=permissions.RESOURCE_ADMIN_MENU
    )
    appbuilder.add_view(
        views.TaskInstanceModelView,
        permissions.RESOURCE_TASK_INSTANCE,