Add ColorCategoryDirective to default theme

Closes #538 (closed)

This allows to build the default theme again by importing ColorCategoryDirective in the default theme. It is kind of useless for the theme though…

I am unsure if this is the right approach.

out of scope It feels like the default theme is a lot of work to maintain and is not used anyhow.
I kind of would propose to get rid of it.
I am uncertain about the usefulness of the theming approach we currently have. It feels like we need to write nearly every component twice. Therefore we can get rid of the default theme and implement a new theme if the necessity arises.

These are some unsorted thoughts. I will try to mention this in a dev standup soonish - once I had time to sort my thoughts