docs: add Headlamp to the Trivy Ecosystem page

[mgalesloot]

Description

Add Trivy Headlamp plugin to eco docs

Checklist

• [x ] I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[CLAassistant]

All committers have signed the CLA.

[mgalesloot]

See discussion #7720