Avoiding inline script tag in built index.html

It would be great if it was possible to avoid having the
```
import init from '/index-....js';init('/index-..._bg.wasm');
```
part of the html in a separate file and load it as a module, similar to React's `INLINE_RUNTIME_CHUNK=false`

This is so allowing script-src 'unsafe-inline' can be avoided when setting Content Security Policy headers.

