Improve JS bundle

All the JS gets bundled into a single file, which is not very good

```
dist/index.html                     1.45 kB │ gzip:   0.60 kB
dist/assets/index-DLQMCBhk.css     19.22 kB │ gzip:   4.48 kB
dist/assets/index-Ia8Pe_fN.js   2,005.63 kB │ gzip: 331.94 kB
```

Not a big issue, but a resolve-satisfying one ^^