Build Storybook statically and push it to GitLab Pages

Problem/Motivation

It'd be easier for us if we could build Storybook statically on CI and push it to GitLab Pages, rather than needing to push to the secondary BitBucket repository for build and deployment by Vercel. I'm pretty sure GitLab CI gives us the flexibility to do this, as long as we don't need too much from GitLab Pages.