Add env variable

Set NODE_ENV to production when publishing to ensure smaller packed size.

package.json

@@ -39,7 +39,7 @@
     "typescript": "^3.9.7"
   },
   "scripts": {
-    "prepublishOnly": "rm -rf dist/ && rollup -c",
+    "prepublishOnly": "NODE_ENV=production rm -rf dist/ && rollup -c",
     "test": "jest",
     "build": "rm -rf dist/ && rollup -c",
     "generate": "plop",