tsconfig.json

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "moduleResolution": "node",
    "declaration": true,
    "declarationDir": "lib",
    "strict": true,
    "outDir": "lib",
    "strictPropertyInitialization": true
  },
  "include": ["src/**/*.ts"]
}