Use as a module or middleware in separated existing express server

[EdgarJeremy]

I don't want my server to be inside of the instance of Tilesplash. In other words, I just want to use the .layer() method and the render() function attached to a completely separated express server.
Say that I have a server configuration like this :

const express = require('express');
const app = express();
app.use('/api', require('./routes/api'));
// ... (a lot of middleware config & routes) ...
app.listen(8080);

It'll be much more convenient if this library can act as a middleware so I can easily access the tile object and the render function attached to the res object like this

app.use(tilesplash({..options}));
app.get('/tile/:x/:y/:z', (req, res)=>{
  // res.render() <-- the render() function
  // res.tile <-- the tile object
})