Add jsdelivr to package.json (#2086)

Author: steffans

Diff for: package.json

@@ -7,6 +7,7 @@
   "main": "dist/vue-router.common.js",
   "module": "dist/vue-router.esm.js",
   "unpkg": "dist/vue-router.js",
+  "jsdelivr": "dist/vue-router.js",
   "repository": {
     "type": "git",
     "url": "https://github.com/vuejs/vue-router.git"