add JRuby 9.3 to CI matrix; upgrade asciidoctor-diagram to 2.2
add JRuby 9.3 to CI matrix; upgrade asciidoctor-diagram to 2.2

mojavelinux/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,mojavelinux/asciidoctor-pdf