mermaid diagrams not rendered in `?print-pdf` mode

[zygoloid]

Steps to reproduce:

Visit https://reveal-hugo.dzello.com/?print-pdf and scroll down to the "mermaid" example.

Expected:

Rendered diagram, like in non-?print-pdf mode.

Actual:

Mermaid graph description "graph LR A --> B B --> C" appears on slide.

[zygoloid]

Workaround

After opening slides in ?print-pdf mode, manually invoke mermaid.init() from JavaScript console before printing.