`pkgdown` implementation for `retractcheck`

It seems like a good idea to use pkgdown to make a cool landing page for the retractcheck package. This will then become the page to reference to.

I am unsure whether the packages contain sufficient information already to do this, because I haven’t looked into this further. Contributions welcome if anyone is interested in helping out :slight_smile:

Damn that was way easier than I expected: pkgdown::build_site() :woman_shrugging: