Update gh-pages build workflow to install asciidoctor to use

Author: sadielbartholomew

.github/workflows/deploy-preview.yml

@@ -28,6 +28,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y \
             asciidoc \
+            asciidoctor \
             dblatex \
             xmlto \
             make