Moving the conditional formatting vignette to an article

[olivroy]

Addresses #786

Since the vast majority of images is in the conditional formatting vignette, I think this is enough to close the issue.

Edit: source https://r-pkgs.org/website.html#vignettes-and-articles

https://r-pkgs.org/website.html#non-vignette-articles

Content that involves a lot of figures, which cause your package to bump up against CRAN’s size constraints. The ggplot2 package presents several FAQs as articles for this reason.