Add OpenSSF Scorecard badge to README

[wnstfy]

Single-line addition: appends an OpenSSF Scorecard badge next to the existing GitHub stars/license/last-commit badges. Score auto-updates from scorecard.dev after each weekly scan.

Badge target: https://scorecard.dev/viewer/?uri=github.com/wnstify/docker (now live — Scorecard's first run completed at 09:43Z when PR #11 merged).

[github-actions]

Trivy misconfiguration findings (HIGH + CRITICAL)

Findings below. Fix the issue or add an ignore entry to .trivyignore with a justification.

Report Summary

┌────────┬──────┬───────────────────┐
│ Target │ Type │ Misconfigurations │
├────────┼──────┼───────────────────┤
│   -    │  -   │         -         │
└────────┴──────┴───────────────────┘
Legend:
- '-': Not scanned
- '0': Clean (no security findings detected)