fix missing attribute reference in README
fix missing attribute reference in README

glamouracademy/asciidoctor,glamouracademy/asciidoctor,pepijnve/asciidoctor,yukisan/asciidoctor,anthonny/asciidoctor,gjtorikian/asciidoctor,neontapir/asciidoctor,mjang/mj-asciidoc,mjang/mj-asciidoc,pepijnve/asciidoctor,neontapir/asciidoctor,benignbala/asciidoctor,yukisan/asciidoctor,anthonny/asciidoctor,asciidocfx/asciidoctor,asciidocfx/asciidoctor,benignbala/asciidoctor,cuit-zhaxin/asciidoctor,gjtorikian/asciidoctor,cuit-zhaxin/asciidoctor