Add plugin and bundle.

composer.json

@@ -33,7 +33,8 @@
     "doctrine/cache": "^1.0"
   },
   "require-dev": {
-    "phpcq/all-tasks": "^1.2"
+    "phpcq/all-tasks": "^1.2",
+    "contao/manager-plugin": "^2.1"
   },
   "autoload": {
     "psr-4": {
@@ -51,12 +52,8 @@
       "dev-develop": "2.1.x-dev",
       "dev-release/3.0.0": "3.0.x-dev"
     },
+    "contao-manager-plugin": "Netzmacht\\Contao\\Leaflet\\ContaoManager\\Plugin",
     "contao": {
-      "sources": {
-        "module": "system/modules/leaflet",
-        "assets/maps": "assets/leaflet/maps",
-        "assets/js": "assets/leaflet/js"
-      },
       "transifex": {
         "project": "contao-leaflet-maps",
         "prefix": "core-",