Adds Headlamp Plugin Catalog installation instructions and a usage
summary to ArtifactHub metadata. Confirms appVersion 0.35.0 is current
(matches latest intel-device-plugins-for-kubernetes v0.35.0 release).
Partial close of #16 (v1.0 readiness checklist) — screenshots remain
blocked pending actual plugin deployment for capture.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>