core/tsconfig.json

{
  "ts-node": {
    "compilerOptions": {
      "module": "CommonJS"
    }
  },

  "files": ["src/index.ts"],
  "compilerOptions": {
    "outDir": "./lib/",
    "noImplicitAny": true,
    "allowSyntheticDefaultImports": true,
    "declaration": true,
    "declarationMap": true,
    "sourceMap": true,
    "module": "ES6",
    "moduleResolution": "Node",
    "target": "ES6",

    "lib": [
      "ESNext",
      "DOM"
    ]
  }
}