Add GitHub Actions workflows for multi-platform releases

[Copilot]

Automates building and publishing RusTalk binaries for Linux x64, macOS x64/ARM64, and Windows x64.

Changes

CI Workflow (.github/workflows/ci.yml)

• Cross-platform testing on push/PR
• Linting and build checks
• Explicit GITHUB_TOKEN permissions

Release Workflow (.github/workflows/release.yml)

• Triggers on version tags (v*) or manual dispatch
• Parallel builds for all platforms
• Packages binary, sample config, README, and LICENSE as tar.gz/zip
• Auto-creates GitHub releases with SHA256 checksums
• Detects pre-releases (tags containing -rc, -beta, -alpha)

Documentation & Tooling

• RELEASE.md: Release process and troubleshooting guide
• scripts/bump-version.sh: Helper for version updates
• Updated README with installation instructions for pre-built binaries

Usage

# Create a release
./scripts/bump-version.sh 0.2.0
git add Cargo.toml Cargo.lock && git commit -m "Bump version to 0.2.0"
git tag -a v0.2.0 -m "Release version 0.2.0"
git push origin main && git push origin v0.2.0

Workflow builds all platforms in ~15-30 minutes and publishes to GitHub Releases.

Original prompt

I'd like to look at publishing a release, and potentially packages. For a release to be viable, I'm guessing we need to compile it using a github runner, and produce a tar.gz of the resulting binaries. I will be guided by best practice on this, but that's the next step I think

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