Preserving YAML metadata blocks in `cast_document`

[jpfairbanks]

I am trying to use Asciicast.jl inside of quarto to make gifs on reveal.js slides. When I run cast_document on my markdown files, the YAML metadata blocks at the top of the file gets stripped out. Is there a way to prevent this behavior? Is it a bug in the pandoc filters that are being used?

[ericphanson]

I think maybe we just need to pass -s to pandoc: https://pandoc.org/chunkedhtml-demo/3.3-general-writer-options.html