…ge (#1958)

@sejas has [brought to our
attention](WordPress/playground-tools#359 (comment))
that the imports of the wasm assets are using incorrect paths, since
3bebb24.

The
[source](https://github.com/WordPress/wordpress-playground/blob/trunk/packages/php-wasm/web/src/lib/get-php-loader-module.ts#L22)
says something like:

```ts
return await import('../../public/php/jspi/php_8_3.js');
```

Which currently results in the built file saying:

```js
return await import("./jspi/php_8_3.js");
```


However, since the tree of the published package is as follows, the path
in the built file is missing a leading `/php`.

```
php
├── asyncify
│   └── php_8_3.js
└── jspi
    └── php_8_3.js
```

This PR fixes the issue by making it so that the imports have a leading
`/php`, which results in the import being:

```js
return await import("./php/jspi/php_8_3.js");
```

## Testing instructions

Build the package:

```shell
npx nx run php-wasm-web:build
```

Then make sure that the paths in `dist/packages/php-wasm/web/index.js`
(around line 95) are correct, i.e. `./php/jspi/php_8_3.js`.