Updated missing url https://cdn.rawgit.com/Leaflet/Leaflet.markercluster/v1.0.0-beta.2.0/dist/leaflet.markercluster.js to https://cdn.jsdelivr.net/gh/leaflet/leaflet.markercluster/v1.0.0-beta.2.0/dist/leaflet.markercluster.js
https://unpkg.com/leaflet@1.0.0/dist/leaflet-src.js
https://unpkg.com/esri-leaflet@2.0.4
https://cdn.rawgit.com/Leaflet/Leaflet.markercluster/v1.0.0-beta.2.0/dist/leaflet.markercluster.js
https://unpkg.com/esri-leaflet-cluster@2.0.0