GH actions: no rmarkdown?

[trevorcampbell]

Every few runs of the github actions workflow results in an error where the runner complains that rmarkdown and knitr aren't installed.

https://github.com/UBC-STAT/stat-406/actions/runs/10860357801/job/30140845043

It doesn't happen every time, so it's probably related to whether built files in _freeze etc are being pushed as well.

[trevorcampbell]

Yep, my guess is probably right: see quarto-dev/quarto-cli#5870

[trevorcampbell]

On the one hand, it may be worth fixing this. OTOH the Stat406 package is so huge that we probably don't want a runner to install it every time it triggers. So probably the best thing to do is either to make a docker image that we can run the workflow on and put it on DockerHub, or to just leave it alone (but document that you need to fully commit all built files to get a working site rebuild)