Get mapping without sync-plugin

[DanSnow]

Checklist

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Is your feature request related to a problem? Please describe.
I want to use relativePositionToAbsoultePosition and absolutePositionToRelativePosition at the websocket server side. These helper functions require a mapping parameter. Currently, I just copy and paste createNodeFromYElement and its related functions from sync-plugin.js but since it's private API. I want to ask is it possible to expose a public API to do get the mapping from Y.js document?

Describe the solution you'd like
Expose a helper function to get the mapping

Describe alternatives you've considered

Additional context

[jamesopti]

This would be useful for us as well to work with relative positions on the server side.

[jjgmckenzie]

Any plans with this in 2023?