Add Docker-Sentinel to Monitoring section

[Will-Luck]

Summary

Adds Docker-Sentinel to the Monitoring section.

Docker-Sentinel is a container update orchestrator written in Go. It provides per-container update policies, automatic rollback on health-check failure, lifecycle hooks (pre/post-update scripts), Prometheus metrics, and a real-time web dashboard with SSE-driven updates. It connects to the Docker API via the official Moby SDK.

Scope

• README entries/content
• Go CLI/tooling
• GitHub workflows or .github docs

If This PR Adds/Edits README Entries

• Category/section touched: Monitoring
• New or updated project links: https://github.com/Will-Luck/Docker-Sentinel

Validation

• Entry is alphabetically ordered (between Docker-Flow-Monitor and DockProc)
• Link points to project repository (no duplicates or redirects)
• Description is concise and specific

Contributor Checklist

• Entries are alphabetically ordered in their section
• Links point to project repositories (no duplicates or redirects)
• Descriptions are concise and specific
• Archived/deprecated projects were removed instead of tagged
• Used :yen: only when applicable

[veggiemonk]

Thank you for your contribution
@Will-Luck could you resolve the conflicts please?
Otherwise this looks good.

[veggiemonk]

resolve merge conflicts

[Will-Luck]

Hi @veggiemonk - I rebased and force-pushed the day after your review (March 18th). The branch is clean against master with no conflicts. Should be good to merge whenever you're ready.