Migrate the documentation engine to Antora 3.0.0

[themr0c]

Antora 2.3 will enter maintenance on January 25, 2022 and reach end of life (EOL) on February 25, 2022. See: https://docs.antora.org/antora/latest/whats-new/#antora-2-3-eol

Consider adding the Lunr search engine after migration. See: https://gitlab.com/antora/antora-lunr-extension/