A11y infrastructure

[akuny]

Add a basic accessibility scan (results excluded from API and snapshot).

[github-actions]

MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	3.31s
✅ GIT	git_diff	yes		no	0.12s
✅ JSON	eslint-plugin-jsonc	2	0	0	3.14s
✅ JSON	jsonlint	2		0	1.05s
✅ JSON	prettier	2	0	0	1.42s
✅ JSON	v8r	2		0	6.09s
✅ TYPESCRIPT	eslint	8	0	0	11.36s

See errors details in artifact MegaLinter reports on CI Job page
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff