remix-project/tsconfig.json

{
    "compilerOptions": {
      /* Basic Options */
      "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
      "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
      "declaration": true,                   /* Generates corresponding '.d.ts' file. */
      "outDir": "./lib",
      "strict": true,                         /* Enable all strict type-checking options. */
      "strictPropertyInitialization": false,  /* Enable strict checking of property initialization in classes. */
      /* Experimental Options */
      "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
      "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
      "typeRoots": [ "./types"]
    },
    "exclude": ["./lib"]
}