Broken user separation for undo/redo

[stippi]

Steps to reproduce in the demo:

• Insert text into the editor of the first user
• Insert text into the editor of another user
• Switch focus back to the editor of the first user
• Invoke "undo", for example via keyboard shortcut

Observed behavior:
The text inserted by the second user is removed, but from within the editor of the first user.

Expected behavior:
Only the text inserted by the first user should be removed. The text inserted later by the second user should be left intact.

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From my understanding, the editor is constructed with withHistory(). It is notable that Y.js itself also provides a solution for a user-separated undo history.

[BitPhinix]

The current version of slate-yjs doesn't offer a history plugin so this is to be expected. The new version (in the next branch) however will.

[stippi]

Nice. Thanks for the update!