This PR replaces the current carousel control chevron icons with the ones from Bootstrap Icons, and then adds a new .carousel-dark
variant. That modifier class uses filter
to invert the SVGs and some additional CSS to change the indicator and caption colors.
Fixes #25360 (closed).
Preview: https://deploy-preview-31650--twbs-bootstrap.netlify.app/docs/5.0/components/carousel/#dark-variant