Building Website Builder editor components, theming, and CMS integration using @webiny/website-builder-nextjs. Use this skill when the developer wants to create editor components for the Website Builder, register components with createComponent, define configurable inputs (text, number, boolean, color, select, file/image, slot, lexical, object, tags), type the component's props correctly (especially file/image inputs, which are objects with { src, width, height, ... } and NOT plain strings, and lexical inputs which are { html, state } objects), set up component groups, customize the theme (CSS variables, createTheme, Tailwind bridge, fonts), build Server Components that fetch CMS data, or understand the WB architecture (Admin iframe + Next.js). Also use for anything related to the Website Builder starter kit.