docs(readme): add banner and use markdown call outs

[beiertu-mms]

Banner created on

• https://liyasthomas.github.io/banner/

with OneDark colors

• https://onedarktheme.com

Replace emoji short code with markdown call outs

• https://github.com/DavidWells/advanced-markdown/#call-outs

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors
✅ REPOSITORY	gitleaks	yes		no
✅ REPOSITORY	git_diff	yes		no
✅ REPOSITORY	grype	yes		no
✅ REPOSITORY	secretlint	yes		no
✅ REPOSITORY	trivy	yes		no
✅ REPOSITORY	trivy-sbom	yes		no
✅ REPOSITORY	trufflehog	yes		no

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

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