Added a way to register JS modules directly

[WebReflection]

This MR provides the ability parse the [js_modules.main] and [js_modules.worker] config entries in a source -> target manner so that it's possible to declare any JS module (as standard ECMAScript Module, aka: ESM) that would be automatically available via polyscript.js_modules reference.

Modules that are on main only and don't have any worker counterpart are fetched on the fly in workers.

Modules that require also companion CSS styles can be defined by providing a .css href and still pointing at the same module name, as that gets resolved lazily as opposite of landing out of the box any CSS that's present in the config.

Example

# file ./modules.toml

[js_modules.main]
"https://cdn.jsdelivr.net/npm/leaflet@1.9.4/dist/leaflet-src.esm.js" = "leaflet"
"https://cdn.jsdelivr.net/npm/leaflet@1.9.4/dist/leaflet.css" = "leaflet"

<div id="worker-map"></div>
<script type="pyodide" config="./modules.toml" worker>
    from polyscript.js_modules import leaflet as L

    center = [51.505, -0.09]
    mark = [51.5, -0.09]
    map = L.map('worker-map').setView(center, 13)

    L.tileLayer(
        'https://tile.openstreetmap.org/{z}/{x}/{y}.png',
        {"attribution": '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'}
    ).addTo(map)

    L.marker(mark).addTo(map).bindPopup('Modules on Worker are awesome 🥳').openPopup()
</script>

The wonderful leaflet has been used to demo both main and worker case.

TODOs

• make this resolution happens
• write documentation around that resolution - edit this should actually happen in PyScript as we link config details to PyScript config resolution