Add missing types property in package.json

Author: Peter Hegman

package.json

@@ -8,6 +8,7 @@
   "browser": {
     "./sfc": "src/Mapbox.vue"
   },
+  "types": "dist/Mapbox.vue.d.ts",
   "repository": {
     "type": "git",
     "url": "https://github.com/phegman/mapbox-gl-vue.js.git"