In case of the end of the node,`relativePositionToAbsolutePosition` conversion error

[Gggpound]

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Checklist

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Describe the bug
When I use relativePositionToAbsolutePosition to create a relative index between a->b based on a certain node, as long as b reaches the end of this node, then the b in a->b obtained by absolutePositionToRelativePosition will be incorrect, with the index position being 1 less than expected.

To Reproduce
Steps to reproduce the behavior:

1. Create a relative position

const fromRel = absolutePositionToRelativePosition(fromRelPure, yXmlElement, mapping)
// to is the xmlElement node`s endPos
const toRel = absolutePositionToRelativePosition(toRelPure, yXmlElement, mapping)

2. Convert relative position to absolute position

const absFrom = relativePositionToAbsolutePosition(doc, xmlElement, createRelativePositionFromJSON(from), mapping)
 
const absFTo = relativePositionToAbsolutePosition(doc, xmlElement, createRelativePositionFromJSON(to), mapping)

Expected behavior
The index conversion is consistent

Screenshots
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Environment Information

• Browser / Node.js [e.g. Chrome, Firefox, Node.js]
• Yjs version and the versions of the y-* modules you are using [e.g. yjs v13.0.1, y-webrtc v1.2.1]. Use npm ls yjs to find out the exact version you are using.

Additional context
Add any other context about the problem here.

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• This issue is a blocker for my project.