diagnostic(frontend): change ChoroplethMap background to red to isolate rendering pipeline

Author: dmichael-fastly

frontend/components/Map/ChoroplethMap.tsx

@@ -90,7 +90,7 @@ export const ChoroplethMap = React.memo(function ChoroplethMap({ data, className
             {
               id: 'background',
               type: 'background',
-              paint: { 'background-color': 'transparent' }
+              paint: { 'background-color': '#ff0000' }
             }
           ]
         },