Issue #3303759 by alansaviolobo, vdsh: clustering on a external geojson data source

            var geojsonLayer = new L.GeoJSON(myFeatures[key], Drupal.leafletBBox.geoJSONOptions);

            // to cluster on external data source, see https://www.drupal.org/project/leaflet_geojson/issues/3303759

            if (typeof L.markerClusterGroup === 'object') {

            if (typeof L.markerClusterGroup === 'function') {

              var markerClusterGroup = L.markerClusterGroup();

              markerClusterGroup.addLayer(geojsonLayer);

              layerGroup.addLayer(markerClusterGroup);