Release Issue

[tlorusso]

• [x] Update documentation with recommendations for color palettes / build pkgdown site with pkgdown::build_site()
• [x] Check / test feature branch
• [x] Merge color palette feature branch into the dev branch
• [x] Check / test dev branch
• [x] Increment version usethis::use_version()
• [x] Document changes usethis::use_newsmd() (change document manually is possible as well)
• [x] merge into master, if everything works well
• [x] Check / test master branch
• [x] Inform users regarding the update (slack)

[Thomas-Caspar-Fischer]

Release 2.3.1 is out