Support component Islands (Astro Islands)

[unional]

https://docs.astro.build/en/concepts/islands/

Islands are rendered in isolation.
That means sharing application instance through DOM state attachment (React Context) does not work.

One solution is to use https://github.com/unional/global-store instead.

Maybe just-web needs to add a gizmo for it?

[unional]

The issue is how can gizmo like reactGizmo supports it.
It need to use global-store, but then other library gizmo like solidGizmo needs to use the same store.

That's why the store should be supplied by just-web.

Either directly in @just-web/app, or
@just-web/states, or
libraries/context (@just-web/context)