**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
category=permissions.RESOURCE_BROWSE_MENU,
    )
    appbuilder.add_view(
        views.TaskRescheduleModelView,
        permissions.RESOURCE_TASK_RESCHEDULE,
        category=permissions.RESOURCE_BROWSE_MENU,
    )
    appbuilder.add_view(
        views.ConfigurationView,
        permissions.RESOURCE_CONFIG,
        category=permissions.RESOURCE_ADMIN_MENU,
        category_icon="fa-user",
    )
    appbuilder.add_view(
        views.ConnectionModelView, permissions.RESOURCE_CONNECTION, category=permissions.RESOURCE_ADMIN_MENU
    )
    appbuilder.add_view(
        views.SlaMissModelView, permissions.RESOURCE_SLA_MISS, category=permissions.RESOURCE_BROWSE_MENU
    )
    appbuilder.add_view(
        views.PluginView, permissions.RESOURCE_PLUGIN, category=permissions.RESOURCE_ADMIN_MENU
    )
    appbuilder.add_view(
        views.ProviderView, permissions.RESOURCE_PROVIDER, category=permissions.RESOURCE_ADMIN_MENU
    )
    appbuilder.add_view(
        views.PoolModelView, permissions.RESOURCE_POOL, category=permissions.RESOURCE_ADMIN_MENU
    )
    appbuilder.add_view(
        views.XComModelView, permissions.RESOURCE_XCOM, category=permissions.RESOURCE_ADMIN_MENU