feat: add Callout component with note/tip/warning/danger variants

mdx-components.tsx

@@ -1,9 +1,11 @@
 import type { MDXComponents } from 'mdx/types'
+import { Callout } from '@/components/ui/Callout'
 
 
 export function useMDXComponents(components: MDXComponents): MDXComponents {
   return {
     ...components,
+    Callout,
     // Typography
     h1: (props) => (
       <h1 {...props} className="scroll-m-20 heading-xl text-ink mt-10 mb-4">