CLI: Add CSP to output `index.html` to prevent XSS attacks

## Specific Demand

The CLI knows all the scripts that are loaded into the app. That is, the app itself and scripts included in `Dioxus.toml`. We can generate a SHA256/384/512 from them, and include that in the CSP.

## Implement Suggestion

This works for me (I tested this on a bundled build, so it's just one JS file and one SHA):
```html

```