Add the option of a prefix path

in my vite project, the html compiles whit a default url, this url is generated depending on some environment variables in the project so is a dynamic url

`http://localhost:4000/assets/index-awd12431.css`

so this CSS file exists in my dist folder but critical can't find the file because it is unable to search for a path with localhost.

so it will be nice to have a prefixPath option, this way it is possible to ignore the prefix and only search for the files in the current path

```ts
generate({
base: './dist',
inline: true,
src: 'index.html',
extract: true,
prefixPath: 'http://localhost:4000'
});
```
this will omit the `http://localhost:4000` part of the import and get this result `/assets/index-awd12431.css`