pkgdown (BS5-based) template files for all mlr* related packages.
All custom changes live in inst/pkgdown/BS5/extra.scss
pkgdown 2.0 recommends to use bslib like notation to set colors and other variables.
This option has been evaluated though looking up the correct naming is tedious and takes an infinite amount of time.
Just overwriting CSS rules in extra.scss seems to be way easier.