Add centralized Snyk security scanning

[fdevans]

This PR adds the centralized Snyk security scanning workflow to enable automated vulnerability detection.

Changes

• Added .github/workflows/snyk-scan.yml workflow
• Configured to run on push and pull requests to main/master branches
• Uses the reusable workflow from rundeck-plugins/.github repository

Benefits

• Automated security vulnerability scanning
• Consistent security configuration across all plugins
• Early detection of security issues

Testing

The workflow will be triggered automatically on:

• Push to main/master branches
• Pull requests to main/master branches
• Manual workflow dispatch

Dependencies

• Requires SNYK_TOKEN and SNYK_ORG_ID secrets to be configured in the repository

[smartinellibenedetti]

Will fix the pipeline first before merging this PR

[Copilot]

Pull Request Overview

This PR adds a centralized Snyk security scanning workflow to enable automated vulnerability detection across the repository. The workflow is configured to run on push and pull requests to main/master branches and leverages a reusable workflow from the rundeck-plugins organization.

Key changes:

• Added GitHub Actions workflow for automated Snyk security scanning
• Configured multiple trigger events including push, pull requests, and manual dispatch
• Integrated with centralized reusable workflow for consistency across plugins

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