Introduce link checker

[valfirst]

it worths to explore options:
https://gitlab.com/antora/xref-validator
https://github.com/owncloud/docs/blob/master/docs/checking-broken-links.md
https://github.com/timaschew/link-checker
https://github.com/Munter/netlify-plugin-checklinks

Originally posted by @valfirst in vividus-framework/vividus#2376 (comment)

[valfirst]

Starting from Antora 3 all invalid internal references are logged:

[14:22:41.467] ERROR (asciidoctor): target of include not found: partial$azure-authentication-invalid.adoc
    file: /.../vividus/docs/modules/plugins/pages/plugin-azure-resource-manager.adoc:18
    source: /.../vividus (refname: add-ability-to-exeute-azure-operations <worktree>, start path: docs)
[14:22:41.478] ERROR (asciidoctor): target of xref not found: commons:variables-more-invalid.adoc#_scopes
    file: /.../vividus/docs/modules/plugins/pages/plugin-azure-resource-manager.adoc
    source: /.../vividus (refname: add-ability-to-exeute-azure-operations <worktree>, start path: docs)

[valfirst]

#25 adds the validation of all internal links. The validation of external links should be done using the same tool, but it should be run by schedule: once a week on Saturday morning