fix: roll back to leaflet 1.3.1

fixes #277

Author: Nicolò Maria Mezzopera

package.json

@@ -23,7 +23,7 @@
     "url": "git://github.com/KoRiGaN/Vue2Leaflet.git"
   },
   "dependencies": {
-    "leaflet": "^1.3.4",
+    "leaflet": "1.3.0",
     "@types/leaflet": "^1.2.11"
   },
   "peerDependencies": {