Implement *_reply for the web

Also, start extracting shared components

website/src/components/TwoColumns.tsx

@@ -0,0 +1,14 @@
+export const TwoColumns = ({ children }: { children: React.ReactNode[] }) => {
+  if (!Array.isArray(children) || children.length !== 2) {
+    throw new Error("TwoColumns expects 2 children");
+  }
+
+  const [first, second] = children;
+
+  return (
+    <section className="mb-8 lt-lg:mb-12 grid lg:gap-x-12 lg:grid-cols-2">
+      <div className="rounded-lg shadow-lg h-full block bg-white p-6">{first}</div>
+      <div className="rounded-lg shadow-lg h-full block bg-white p-6 mt-6 lg:mt-0">{second}</div>
+    </section>
+  );
+};