Show tag counts in tag index page, clarify docker-compose usage, and update README for local/dev workflows

[dannystaple]

Fixes #27

[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ BASH	bash-exec	1		0	0	0.0s
✅ BASH	shellcheck	1		0	0	0.05s
⚠️ BASH	shfmt	1		1	0	0.0s
❌ C	cppcheck	8		8	0	0.2s
❌ CPP	cppcheck	8		8	0	0.2s
✅ JSON	npm-package-json-lint	yes		no	no	0.39s
✅ JSON	v8r	11		0	0	8.46s
❌ MARKDOWN	markdown-link-check	732		211	0	37.37s
✅ REPOSITORY	gitleaks	yes		no	no	13.79s
✅ REPOSITORY	git_diff	yes		no	no	0.14s
✅ REPOSITORY	grype	yes		no	no	30.92s
✅ REPOSITORY	secretlint	yes		no	no	38.82s
✅ REPOSITORY	syft	yes		no	no	1.55s
✅ REPOSITORY	trivy-sbom	yes		no	no	3.05s
✅ REPOSITORY	trufflehog	yes		no	no	4.4s
✅ XML	xmllint	1		0	0	178.74s
✅ YAML	v8r	12		0	0	9.22s

See detailed report in MegaLinter reports

[dannystaple]