chore: use files field instead of .npmignore

Author: haoqunjiang

.npmignore

@@ -3,6 +3,10 @@
   "version": "4.0.0",
   "description": "eslint-config-typescript for vue-cli",
   "main": "index.js",
+  "files": [
+    "index.js",
+    "recommended.js"
+  ],
   "publishConfig": {
     "access": "public"
   },