feat(ext): draft extension structure (single-page mode)

packages/extension/src/components/ui/spinner.tsx

@@ -0,0 +1,16 @@
+import { Loader2Icon } from 'lucide-react'
+
+import { cn } from '@/lib/utils'
+
+function Spinner({ className, ...props }: React.ComponentProps<'svg'>) {
+	return (
+		<Loader2Icon
+			role="status"
+			aria-label="Loading"
+			className={cn('size-4 animate-spin', className)}
+			{...props}
+		/>
+	)
+}
+
+export { Spinner }