Add shared CI and security baseline

[dejaguarkyng]

Summary

• add reusable Node and static PR CI workflows
• add workflow templates, Dependabot for Actions, supported default issue/PR template locations, SUPPORT, and a CI/CD roadmap
• tighten contribution and security reporting guidance

Validation

• git diff --check
• python3 -m json.tool workflow-templates/node-pr-ci.properties.json
• python3 -m json.tool workflow-templates/static-pr-ci.properties.json
• ruby YAML parse for issue templates, Dependabot, reusable workflows, PR CI, and workflow templates

Security

• PR CI uses least-privilege contents: read permissions
• no secrets are passed to workflows
• external actions are pinned to full commit SHAs
• no deployment or publishing workflow is introduced