The file fqar.Rmd is generated from the fqar text file using:
knitr::knit("vignettes/fqar", output = "vignettes/fqar.Rmd")
following the recommendation from Jeroen Ooms at ROpenSci
(https://ropensci.org/blog/2019/12/08/precompute-vignettes/)

A few changes have to be made manually to the knitted document
- {r eval = FALSE} to all chunks
- fix paths to figure files, which do not appear in a folder
