Also copy the document attributes over and re-use them so any variables that need to be resolved are there. Code copied from https://github.com/asciidoctor/asciidoctor-extensions-lab/blob/master/scripts/asciidoc-coalescer.rb
Also copy the document attributes over and re-use them so any variables that need to be resolved are there. Code copied from https://github.com/asciidoctor/asciidoctor-extensions-lab/blob/master/scripts/asciidoc-coalescer.rb