RFC/ENH importmap not supported on some machine

[Xinyu-Li-123]

I was testing Deskulpt on a Ubuntu20 virtual machine, and I find that importmap is unsupported by the version of webview I am using. I think we should directly replace @deskult-test/xxx with relative path, instead of relying on importmap to resolve named import. We are already doing this with @deskulpt-test/apis, which is replaced with a blob url, we might as well do it for all default dependencies.

I think we could create a hash map that maps named imports of default dependencies to the corresponding relative path. For example,

{
    "@deskulpt-test/react": "/assets/src/.scripts/react.js",
    "@deskulpt-test/raw-apis": "/assets/src/.scripts/raw-apis.js",
    "@deskulpt-test/apis": "/assets/src/.scripts/apis.js",
}

Based on whether we are building or developing, we can load different maps (what importmapPlugin does currently).