Improve default block quote indentation.
Add default left indention to blockquote.
Bootstrap Reboot (which Guise Skeleton uses as a reset) in v4.1.3 doesn't provide a useful <blockquote> style:
Provide at least some left indentation, e.g.:
There's probably no need to provide CSS variables, as this is not a Guise Skeleton component; normal CSS selection and property setting should suffice.