Add Windows and macOS to build and test workflow

[Copilot]

Extends the CI matrix to run on ubuntu-latest, macos-latest, and windows-latest.

• Build: cargo build --verbose runs on all three platforms
• Example tests: Run on Linux and macOS only — examples use GNU/LLVM toolchains which aren't available by default on Windows runners
• Toolchain install: apt install build-essential scoped to Linux; macOS runners ship with clang/gcc pre-installed
• Security: Added permissions: contents: read to follow least-privilege principle

strategy:
  matrix:
    os: [ubuntu-latest, macos-latest, windows-latest]

Original prompt

我想让build and test工作流添加Windows平台和MacOs的支持

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.