R: Vignettes and other documentation

# Vignettes and other documentation

## Vignettes from package 'pdqr'

pdqr::pdqr-01-create |  | Create pdqr-functions with `new_*()` | HTML | source | R code
pdqr::pdqr-02-convert |  | Convert pdqr-functions with `as_*()` | HTML | source | R code
pdqr::pdqr-03-transform |  | Transform pdqr-functions with `form_*()` and base operations | HTML | source | R code
pdqr::pdqr-04-summarize |  | Summarize pdqr-functions with `summ_*()` | HTML | source | R code