Adding Observation Zones to MWAC

[rustynwac]

MWAC had some zones added midseason to their Obs only. They are hoping the app can be updated to reflect what's happening on their website.

[stevekuznetsov]

These get exposed as alternate_zones in the widget config, we need to download the KML, parse it and use those zones.

$ curl -s https://api.avalanche.org/v2/public/avalanche-center/BTAC | jq --raw-output .widget_config.observation_viewer.alternate_zones
https://nac-web-platforms.s3.us-west-1.amazonaws.com/assets/kml/BTAC_AlternateZones_241202.kml
$ curl -s https://api.avalanche.org/v2/public/avalanche-center/MWAC | jq --raw-output .widget_config.observation_viewer.alternate_zones
https://www.mountwashingtonavalanchecenter.org/wp-content/uploads/obs-kml/MWAC_observation_zones011825.kml

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