Support time-series popup for MultiPolygonSeries covjson

- Currently, the playground does not show a popup for `MultiPolygonSeries` covjson files and instead displays a `No data` popup when a polygon is clicked.
- This change fixes that

src/main.js

@@ -204,7 +204,7 @@ function isVerticalProfile (cov) {
 }
 
 function isTimeSeries (cov) {
-  return cov.domainType === C.COVJSON_POINTSERIES || cov.domainType === C.COVJSON_POLYGONSERIES
+  return cov.domainType === C.COVJSON_POINTSERIES || cov.domainType === C.COVJSON_POLYGONSERIES || cov.domainType == C.COVJSON_MULTIPOLYGONSERIES
 }
 
 function createLayer(cov, opts) {