Try installing mermaid

Signed-off-by: Robert Young <[email protected]>

Author: robobario

.github/workflows/asciidoctor-ghpages.yaml

@@ -14,4 +14,5 @@ jobs:
         with:
           source_dir: docs/
           asciidoctor_params: "--require asciidoctor-diagram --attribute=sectlinks --attribute=sectanchors"
+          pre_build: 'apk add nodejs npm && npm install -g @mermaid-js/mermaid-cli'
           post_build: 'find . -name "*.svg" -exec git add -f {} \;'