docs: add Trivy scan badges (!141) · Merge requests · to be continuous... / Docker · GitLab

From an original idea from @gbonnefille 🙏

What do you think @cedric3.olivier @girijasa @clement.bois @beber80 @marc.b.orange ?

See result here: https://gitlab.com/to-be-continuous/docker/-/blob/docs/add-trivy-badges/README.md?ref_type=heads