feat(site): new home page, docs, and design system (#566)

Co-authored-by: Darius Cepulis <dcepulis@mux.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

site/src/hooks/useIntersection.ts

@@ -0,0 +1,27 @@
+import { useEffect, useRef, useState } from 'react';
+
+export function useIntersection(options?: IntersectionObserverInit): [React.RefCallback<Element>, boolean] {
+  const [isIntersecting, setIsIntersecting] = useState(false);
+  const observerRef = useRef<IntersectionObserver | null>(null);
+
+  useEffect(() => {
+    return () => observerRef.current?.disconnect();
+  }, []);
+
+  const ref = (node: Element | null) => {
+    observerRef.current?.disconnect();
+
+    if (!node || isIntersecting) return;
+
+    observerRef.current = new IntersectionObserver(([entry]) => {
+      if (entry?.isIntersecting) {
+        setIsIntersecting(true);
+        observerRef.current?.disconnect();
+      }
+    }, options);
+
+    observerRef.current.observe(node);
+  };
+
+  return [ref, isIntersecting];
+}