Add license and sourcemap generation

rollup.config.ts

@@ -12,7 +12,7 @@ const config = {
     format: 'es',
     sourcemap: true
   },
-  plugins: [typescript(), nodeResolve(), commonjs()]
+  plugins: [typescript(), nodeResolve({ preferBuiltins: true }), commonjs()]
 }
 
 export default config