Single watcher for multiple keys

Feature Request

This snippet allows for watching a single item:
https://github.com/wxt-dev/wxt/blob/c0aa12089e24c9f0cb01fb3f8546f17096b21341/packages/wxt/src/storage.ts#L434-L447

I also wish to have a watcher setup like this:

const unwatch = storage.watch({
  "local:item1"((newValue, oldValue) => {...}),
  "local:item2"((newValue, oldValue) => {...})
});
unwatch();

Is your feature request related to a bug?

N/A

What are the alternatives?

storage.watch("local:item1", (newValue, oldValue) => {...});
storage.watch("local:item2", (newValue, oldValue) => {...});

Additional context

This functionality is available in Plasmo

Start in packages/wxt/src/storage.ts at lines 434-447, where the existing single-item watcher is implemented. Trace its callback and cleanup behavior, then determine how the proposed map of keys to callbacks should preserve those semantics. Done means one watcher can register both local:item1 and local:item2 callbacks and the returned unwatch function removes them.