Display filenames in docs

[maelle]

@Nenuial see

https://rstudio.github.io/config/

source https://github.com/rstudio/config/blob/main/README.Rmd

[Nenuial]

Oh, that's interesting! Especially since my attempt to have pkgdown add this feature was dismissed!

I'll look into it. It looks like it uses a knitr hook to create the labels. I need to take a closer look at how this is done and how we could implement it.

[joelnitta]

Would filename work?