some packages needs esnext feature

Johnwook Choi · Johnwook Choi · commit f5dfc6a74c1d · 2018-01-30T22:51:57.000+09:00
diff --git a/tsconfig.json b/tsconfig.json
@@ -1,6 +1,7 @@
 {
   "compilerOptions": {
     "importHelpers": true,
+    "lib": ["esnext"],
     "module": "commonjs",
     "noUnusedLocals": true,
     "noUnusedParameters": true,
