Website requires some love

[SHAESEN2]

1. Group functions together in the reference section
2. Add a section for the datasets
3. After added learn tutorial from Tim #336 and Integrate learnR vignette and shinyapps.io autodeploy  #339 have been merged, it'd be cool to split our vignettes by "static" and "interactive"

[timtreis]

Re 3: We're now automatically deploying the interactive learnR vignette to shinyapps.io from the development branch. However, this vignette was primarily prepared for a few workshops/show-case we gave in 2021. Therefore, it basically just contains everything we had at that time. It cool be cool to split it into case-studies and have those as "interactive vignettes" (?) on our doc page.