update release workflow to publish ruby gem automatically

[rei-moo]

All PRs:

• Has tests
• Documentation updated

Adding a new header

Generally, adding a new header is always OK.

• Is the header supported by any user agent? If so, which?
• What does it do?
• What are the valid values for the header?
• Where does the specification live?

Adding a new CSP directive

• Is the directive supported by any user agent? If so, which?
• What does it do?
• What are the valid values for the directive?

[Copilot]

Pull request overview

This PR updates the GitHub release workflow to automatically publish the secure_headers Ruby gem to RubyGems when a version tag is pushed. The workflow leverages GitHub's OIDC authentication to securely publish to RubyGems without requiring stored API tokens, which aligns with the gem's MFA requirements.

Changes:

• Added id-token: write permission to enable OIDC authentication for RubyGems publishing
• Added steps to checkout code, set up Ruby environment, and publish the gem using rubygems/release-gem@v1

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