[WIP] Collaborative editing documentation

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original issue description:

Prepare documentation for "Collaborative editing" feature.

Use data available in: https://github.com/ibexa/collaboration/

Original prompt

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This section details on the original issue you should resolve

<issue_title>Collaborative editing documentation</issue_title>
<issue_description>Prepare documentation for "Collaborative editing" feature.

Use data available in: https://github.com/ibexa/collaboration/</issue_description>

<agent_instructions>create a skeleton for a the collaboration feature.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #13

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