[Feature]: Allow appendTo as an array or glob pattern

[SuddenDev]

Hi, I'm currently working with a Laravel Inertia setup and I'm using a multi build setup. Meaning that I have two entry files for different domains (public / backend).

Currently it's impossible to register both with the appendTo option in the Vite Plugin, but I think it would be a good addition. Optionally we could also maybe use a glob pattern instead, but both would be an improvement imo.

Is this possible and wanted? If so, I can also submit a PR. Thanks!