The accessibility-checker package provides CI tools for Node and Karma. These tools started out as server-based checkers about a decade ago, but not all DOMs are serializable and you lose a lot of the CSS context that's needed to do proper evaluation. It's fine for fairly static pages, but has a lot of potential for false positives/negatives.

The tools provide checking for WCAG 2.0 AA, WCAG 2.1 AA and the IBM checklist. The IBM checklist is basically WCAG 2.1 AA, but has some more strict requirements for defining landmarks for screen reader navigation.