New check for vignettes

[mpadge]

Because Dev Guide clearly requires them, as discussed in this software-review-meta issue (link thanks to @maelle ).

[mpadge]

@maelle This should even be somewhat easier because the information is already there:

pkgcheck/R/checks-pkgstats.R

Line 58 in a4eb980

num_vignettes = unname (s$vignettes [1]),

That then forms the start of the main list here

pkgcheck/R/pkgcheck-fn.R

Lines 15 to 16 in a4eb980

	s <- pkgstats_checks (path)
	out <- s$out

And within that function there's this:

pkgcheck/R/pkgcheck-fn.R

Line 76 in a4eb980

out$summary <- pkgchk_pkgstats_summary (s)

which collates the list of numbers of objects including vignettes. Admittedly kinda convoluted like that, but at least the data are already there, and you can just do vignette steps 4-6, and not worry about 1-3. The value you need for those is then checks$summary$num_vignettes.