Set up Nix cache

Version updated for zombiezen/setup-nix-cache-action to version v0.3.0.

• This action is used across all versions by 4 repositories.

Go to the GitHub Marketplace to find the latest changes.

Release notes

What’s Changed

• Add option to use nixcached for uploading and downloading. This can simplify usage of Google Cloud Storage (see README for details).
• Upgrade to Node.js 20.

Full Changelog: https://github.com/zombiezen/setup-nix-cache-action/compare/v0.2.0...v0.3.0

• zombiezen
• GitHub Actions