refactor(core): convert i18n to TS

Author: alaibe

npm-shrinkwrap.json

@@ -166,7 +166,9 @@
   "devDependencies": {
     "@babel/cli": "7.1.2",
     "@babel/plugin-proposal-optional-chaining": "7.0.0",
+    "@types/i18n": "0.8.3",
     "@types/node": "10.11.7",
+    "@types/os-locale": "2.1.0",
     "babel-plugin-dynamic-import-node": "2.2.0",
     "chai": "4.1.2",
     "cross-env": "5.2.0",