add note about image scaling to fopub script
add note about image scaling to fopub script

asciidoctor/asciidoctor-fopub,asciidoctor/asciidoctor-fopub,getreu/asciidoctor-fopub,getreu/asciidoctor-fopub,asciidoctor/asciidoctor-fopub,getreu/asciidoctor-fopub