docs: update related projects

[Moskize91]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

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Run ID: acea670f-aebd-4136-978f-d4c30a9356af

📥 Commits

Reviewing files that changed from the base of the PR and between 885b133 and 16087c9.

📒 Files selected for processing (2)

• README.md
• README_zh-CN.md

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Summary by CodeRabbit

Documentation

• Simplified the related projects section in documentation
• Added SpineDigest as a new related project
• Updated PDF Craft description with revised workflow details and demo video link

Walkthrough

The "Related Projects" section in both English (README.md) and Chinese (README_zh-CN.md) versions was restructured. A dedicated "PDF Craft" subsection was consolidated into a single bullet-point entry with updated workflow description and demo video reference. A new related project entry for "SpineDigest" was added to describe EPUB structural analysis capabilities.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	No description was provided by the author, making it impossible to assess relevance to the changeset.	Add a pull request description explaining the motivation for updating the related projects section and the rationale for adding SpineDigest.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title follows the required format and clearly summarizes the main change: updating documentation about related projects.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch docs

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