Ideas for automatically fetching files on the web
Thanks to Pyxel's new utility script, an html file for Pyxel is very simplified like [this](https://github.com/kitao/pyxel/blob/main/wasm/pages/01_hello_pyxel.html).

Another thing I would like to achieve is automatic fetching of files.
It seems that Emscripten can't mount real file system directly, but it may be realized virtually if I can insert some hook script for each load function in Pyxel.

With the feature, I would like shorten this script from

```html
<body>
    <div id="loading">Loading...</div>
    <pyxel-asset name="assets/pyxel_logo_38x16.png"></pyxel-asset>
    <pyxel-run root="../../python/pyxel/examples" name="01_hello_pyxel.py"
        onstart="document.getElementById('loading').remove()"></pyxel-run>
</body>
```

to
```html
<body>
    <div id="loading">Loading...</div>
    <pyxel-run root="../../python/pyxel/examples" name="01_hello_pyxel.py"
        onstart="document.getElementById('loading').remove()"></pyxel-run>
</body>
```

If anyone has the knowledge to implement this feature, I would appreciate any advice.