[Accessibility issue] Vignettes lacks alt= in plots

[MichaelChirico]

We have a tool that flags images that lack an alt= attribute. See https://help.siteimprove.com/support/solutions/articles/80000863904-accessibility-image-alt-text-best-practices -- these are essential for conveying the image contents to users on screen readers.

You can add these to your vignettes by using the recent-ish fig.alt chunk option in knitr; see https://www.rstudio.com/blog/knitr-fig-alt/.

The vignette at issue is https://github.com/tidyverts/fable/blob/79d5a5049a24ea55dd5d8009259b8ebcea8a4e98/vignettes/fable.Rmd.

Unfortunately the lines are flagged in the HTML output, which won't correspond exactly to the .Rmd file lines, but I assume if you're familiar with the vignette it will be clear which images need it:

fable/inst/doc/fable.html:378
fable/inst/doc/fable.html:579