[TASK] Create CSS Styled Content TypoScript configuration for 6.0

For backwards compatibility we keep versions of the CSS Styled
Content TypoScript configuration files selectable as rendering
template.

The current setup.txt and constants.txt are just copied into
the 6.0 folder. After this change the branches may diverge

Resolves: #44963
Releases: 6.1
Change-Id: I3eef95b796f7f05bb176044ee556a7bf6ab270a7
Reviewed-on: https://review.typo3.org/17830
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert