Add Dependabot configuration for automated dependency updates

[sgaunet]

Summary

Add a Dependabot configuration file (.github/dependabot.yml) to enable automated dependency updates for this project.

Motivation

• Automated dependency updates help keep the project secure by promptly applying security patches
• Reduces manual effort in maintaining up-to-date dependencies
• Improves project maintenance and security posture

Proposed Configuration

The configuration should include:

• Go modules: Monitor go.mod for Go dependency updates
• GitHub Actions: Monitor workflow dependencies
• Docker: Monitor Dockerfile dependencies (if applicable)

Suggested Schedule

• Go modules: Weekly updates
• GitHub Actions: Monthly updates
• Docker: Monthly updates

Additional Considerations

• Set appropriate pull request limits to avoid overwhelming maintainers
• Consider grouping related updates to reduce PR noise
• Enable auto-merge for patch-level security updates (optional)

Implementation

Create .github/dependabot.yml with appropriate ecosystem configurations based on project needs.