Update package.json

Author: kaorun343

package.json

@@ -24,6 +24,7 @@
   "devDependencies": {
     "@types/node": "^8.0.47",
     "ava": "^1.2.1",
+    "reflect-metadata": "^0.1.13",
     "rollup": "^0.50.0",
     "rollup-plugin-commonjs": "^8.2.6",
     "rollup-plugin-typescript": "^0.8.1",