docs(readme): add demo video section to both READMEs

[BlackHole1]

Adds a short Demo section to both the English and Chinese READMEs so a reader can see dockswipe driving macOS dock-swipe gestures from the terminal before working through the rationale below it. The clip lives under assets/demo.mp4 and is referenced over the GitHub raw URL so it plays inline on the rendered README instead of depending on an external host.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 3e78217d-ccf3-4918-af40-994850c4acc5

📥 Commits

Reviewing files that changed from the base of the PR and between 8cee152 and f30b6f1.

⛔ Files ignored due to path filters (1)

• assets/demo.mp4 is excluded by !**/*.mp4

📒 Files selected for processing (2)

• README.md
• README.zh-CN.md

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Summary by CodeRabbit

• Documentation
  • Added a new “Demo” section to the README with a brief description and an embedded demo video.
  • Added a corresponding “演示” section to the Chinese README, including a demo video showing the app in action.

Walkthrough

The English and Chinese README files each add a new Demo/演示 section. Both sections include descriptive text about terminal-driven dock-swipe gestures and embed a demo video sourced from the repository asset.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title matches the required type(scope): subject format and accurately summarizes the README demo video update.
Description check	✅ Passed	The description clearly matches the documentation changes by describing the new demo section and embedded video in both READMEs.
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/readme-demo-video

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