`html_vignette` v `html_format`

[TimTaylor]

For vignettes, do you still advise using html_vignette versus html_format? The main difference I've observed is that html_vignette does not seem to allow embedding of https resources.

FI - I've also found that pkgdown can handle html_format but not html_vignette. I'm aware this is more a consideration for pkgdown authors than yourself but just wanted to flag for awareness.