existsSync is not exported

With this configuration:

```node
import copy from "rollup-plugin-copy";
import sucrase from "@rollup/plugin-sucrase";
import json from "@rollup/plugin-json";
import css from "rollup-plugin-css-only";
import resolve from "@rollup/plugin-node-resolve";
import svg from "rollup-plugin-svg";
import nodePolyfills from 'rollup-plugin-node-polyfills';

export default {
input: "src/index.jsx",
output: {
file: "dist/index.js",
format: "iife",
globals: {
react: "React",
fs: "fs",
path: "path",
"react-dom": "ReactDOM",
},
},
//This is meant to suppress the warning for d3-selection circular dependencies (https://github.com/d3/d3-selection/issues/168)
onwarn: function (warning, warn) {
if (warning.code === "CIRCULAR_DEPENDENCY") return;
warn(warning);
},
plugins: [
svg(),
css({ output: "css/bundle.css" }),
json(),
nodePolyfills(),
sucrase({
transforms: ["jsx"],
production: true,
}),
copy({
targets: [
{
src: [
"node_modules/react/umd/react.development.js",
"node_modules/react-dom/umd/react-dom.development.js",
"src/static/*",
],
dest: "dist",
},
],
verbose: true,
}),
resolve(),
],
external: ["react", "react-dom"],
};
```
I get this error

```
[!] Error: 'existsSync' is not exported by node_modules/rollup-plugin-node-polyfills/polyfills/empty.js, imported by ../../core/utils/silly-i18n/src/index.js
```

It's true that the documentation mentions

> optional, add option to enable browserified shim

However, not clear how to add that option. What does it really mean?