[FEAT] support watch meta change in storage

Feature Request

Now we only support to watch the value of the local storage. But can't watch the change of the metadata of local storage variable.

What are the alternatives?

Now we have to add $ at the end of the KEY local:someKey$ to watch its metadata. But in the future, the underline implementation of the meta may change, and may should not add $.

This is the work around of my code

  // Add $ to the key to get the meta key for LAST_SYNCED_CONFIG_STORAGE_KEY
  const metaKey = `local:${LAST_SYNCED_CONFIG_STORAGE_KEY}$`

  const unwatch = storage.watch<LastSyncedConfigMeta>(metaKey, (_, newMeta) => {
    const meta = newMeta
    setAtom(meta?.lastSyncedAt ?? null)
  })

Additional context

Add any other context or screenshots about the feature request here.

Start by tracing the storage.watch API and its handling of local storage keys, including the current local:someKey$ metadata convention. Define the metadata-watch behavior without requiring the $ suffix, while preserving existing value watching; done means callers can observe metadata changes through the storage API.