added files item to package.json

Author: VirtualParticle

package.json

@@ -5,6 +5,7 @@
   "module": "./lib/esm/index.js",
   "types": "./lib/esm/index.d.ts",
   "license": "MIT",
+  "files": ["./lib"],
   "scripts": {
     "build": "yarn build:esm && yarn build:cjs",
     "build:esm": "tsc",