tsconfig.json

{
  "include": ["src/**/*.ts"],
  "compilerOptions": {
    /* Language and Environment */
    "target": "ES2018",

    /* Modules */
    "module": "commonjs",                                /* Specify what module code is generated. */

    /* Emit */
    "declaration": true,                              /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
    "sourceMap": true,                                /* Create source map files for emitted JavaScript files. */
    "outDir": "./lib",                                   /* Specify an output folder for all emitted files. */

    /* Interop Constraints */
    "esModuleInterop": true,                         /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */

    /* Type Checking */
    "strict": true,                            /* Enable error reporting for expressions and declarations with an implied `any` type.. */
    "strictNullChecks": true,                         /* When type checking, take into account `null` and `undefined`. */
    "strictFunctionTypes": true,                            /* Ensure 'use strict' is always emitted. */
    "noUnusedLocals": true,                           /* Enable error reporting when a local variables aren't read. */
    "noImplicitReturns": true,                        /* Enable error reporting for codepaths that do not explicitly return in a function. */
    "skipLibCheck": true                                 /* Skip type checking all .d.ts files. */,
  }
}