docs: group README maintenance and license sections

[aoirint]

Warning

This pull request was created with assistance from LLMs.

Summary

• Moves the README maintenance link into a Maintenance section near the end of the document.
• Groups the release procedure under Maintenance as ### Release procedure.
• Keeps the license section after maintenance so project and bundled upstream license information stay visible but separate from usage docs.

Related Issues

None

Notes for reviewers

AI disclosure

Codex reorganized the README headings and checked the resulting Markdown diff for scope and whitespace issues.

Testing

Automated checks

• git diff --check

AI-assisted inspections

• Request: Check that README maintenance, release, and license sections are grouped consistently.
  • AI-assisted result: The README now presents usage first, maintenance/release information together, and license information afterward without changing project behavior.