gh-4379: Link target release to release PEP in PEP 0

[BHUVANSH855]

Summary

This change links Python version entries in PEP 0 to their corresponding release schedule PEPs.

Specifically, it:

• Builds a mapping from Python versions to release schedule PEP numbers using release-topic metadata.
• Emits :pep: references for Python version entries when a matching release schedule PEP exists.
• Falls back to plain text when no matching release schedule PEP is available.
• Adds a regression test covering the new linking behavior.

Testing

python -m pytest
python build.py

Results:

• 532 passed, 2 xfailed
• Documentation build succeeded

Issue

Closes #4379

[read-the-docs-community]

Documentation build overview

📚 pep-previews | 🛠️ Build #33757148 | 📁 Comparing bfc2b35 against latest (9bb3132)

  🔍 Preview build  

4 files changed

± index.html
± numerical/index.html
± pep-0000/index.html
± pep-0764/index.html