Add system output type

[jamesarosen]

WebPack has built-in compatibility with SystemJS. As of May 2023, rspack's output.library.type supports many values, but not system.

SystemJS, while not standards-track, is widely used, especially in micro-frontend systems like single-spa.

One caveat is that SystemJS imports are context-sensitive, which is why things like systemjs-webpack-interop exist.

If the rspack team would prefer this as a plugin, it would be helpful to have a reference plugin for supporting a new output.libraryTarget (or output.library.type).

[jamesarosen]

For now, a workaround is to use libraryTarget: "amd" and SystemJS's AMD plugin.

[hardfist]

yes system format is widely used in micro-frontend, we may support it in the future, I create a issue to be tracked here #3112