Bump version to 0.4.0 as Leaflet<1.0 won't be supported anymore

Author: vogdb

package-lock.json

@@ -1,6 +1,6 @@
 {
     "name": "leaflet.select-layers",
-    "version": "0.3.1",
+    "version": "0.4.0",
     "description": "a Leaflet plugin which adds new control to switch between different layers on the map. New control extends L.Control.ActiveLayers and replaces radio button panel with select tag.",
     "scripts": {
         "dev": "webpack --watch --mode=development",