Show warning area

[tattii]

• emergency
• warning
• advisory
• none
  https://github.com/weatherbox/jma-xml/blob/master/functions/atomfeed/warningxml.py#L81

MapboxGL

• join data https://www.mapbox.com/mapbox-gl-js/example/data-join/
  categorical x 1 layer
• filter in https://www.mapbox.com/mapbox-gl-js/style-spec/#types-filter
  filter in x 3layer