Docs: add ci workflow for building Sealos Docs Site Docker image

[yangchuansheng]

🤖 Generated by Copilot at 57007a9

Summary

📄🐳🌐

This pull request adds a new Dockerfile and a GitHub Actions workflow for the Sealos Docs Site. The Dockerfile builds a multi-platform image that serves the website with brotli compression. The workflow builds and pushes the image to three registries on demand or on changes to the docs folder.

Sealos Docs Site:
Docker image for all platforms
Winter of content

Walkthrough

• Add a new workflow file for GitHub Actions to build and push a Docker image for the Sealos Docs Site (link)
• Add a new Dockerfile for the Sealos Docs Site that uses a multi-stage build (link)

[sealos-ci-robot]

🤖 Generated by lychee action

Summary

Status	Count
🔍 Total	956
✅ Successful	375
⏳ Timeouts	0
🔀 Redirected	0
👻 Excluded	580
❓ Unknown	0
🚫 Errors	0

Full action output

Full Github Actions output

[sweep-ai]

Apply Sweep Rules to your PR?

• Apply: Leftover TODOs in the code should be handled.
• Apply: All new business logic should have corresponding unit tests in the tests/ directory.
• Apply: Any clearly inefficient or repeated code should be optimized or refactored.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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