message: add engines field
diff: {
  "name": "tsjs-lib-generator",
  "private": true,
  + "engines": {
  + "node": ">=15"
  + },
  "scripts": {
  "build": "tsc -p ./tsconfig.json && node ./lib/index.js",
  "fetch-idl": "tsc -p ./tsconfig.json && node ./lib/idlfetcher.js",
  