Reactive update plugin

[strdr4605]

We have a collaborative app. For reactivity of our lexical state, we tried LexicalCollaborationPlugin, but after a couple of months of using it, we had some bugs/strange behaviors with our custom y-websocket server.
In the end, we decided to move from LexicalCollaborationPlugin to a custom ReactiveUpdatePlugin that updates the editor state based on a timestamp difference between the local state and server state, also keeping the cursor.

Of course, it is not the same feature-rich as LexicalCollaborationPlugin, and it may have some different behavior but it's working nicely for us.

I was thinking that other projects may also benefit from using this plugin, in case they need simple reactivity (and not the whole feature set of LexicalCollaborationPlugin and managing y-websocket server)

However, the implementation relies on the local state and a timestamp (when serializedEditorState was changed) field in DB alongside serializedEditorState.

To makeReactiveUpdatePlugin a plug-and-play, would be nice to have this timestamp stored inside serializedEditorState (most likely in RootNode? Or maybe a decorator node that will always stay in the serializedEditorState?🤔)

If there are some ideas on how to persist this timestamp in the EditorState and serializedEditorState, I may try them with our implementation of ReactiveUpdatePlugin and submit a PR with new plugin.

cc @ivailop7 @etrepum

[etrepum]

Storing metadata on the root node will be possible after #7117

[strdr4605]

Ok, I will follow the PR, and when the new version is release, I will play with it.