getOrCreateWsChannel: recreate channel after it expires

[srosset81]

Currently, once a WebSocket channel expires, the frontend just stops listening and no message is provided to the user.

https://github.com/assemblee-virtuelle/semapps/blob/master/src/frontend/packages/semantic-data-provider/src/notificationChannels/subscribeToUpdates.ts#L135-L140

If the tab is visible (!document.hidden), or when it becomes visible again (using the visibilitychange event), we should probably recreate a WebSocket channel.