Express server with adding HTTP headers

server.js

const express = require('express');

const path = require('path');

const app = express()
const PORT = process.env.port || 4000

app.use((req, res, next) => {
    res.setHeader('referrer-policy', 'strict-origin-when-cross-origin');
    next();
});

app.get('*', (req, res) => {
    res.sendFile(path.resolve(__dirname, 'static/index.html'));
});

app.listen(PORT, function () {
    console.log(`Server works on PORT ${PORT}`)
});

You also need to create static folder and put there your index.html file