feat(frontend): incomplete port to next.js

frontend/components/NavItem.tsx

@@ -0,0 +1,24 @@
+import { ReactNode } from "react";
+import Link from "next/link";
+
+export interface Props {
+  children?: ReactNode | undefined;
+  href: string;
+  plain?: boolean | undefined; // Do not wrap in <li></li>
+}
+
+export default function NavItem(props: Props) {
+  const ret = (
+    <Link
+      className="hover:text-sky-500 dark:hover:text-sky-400"
+      href={props.href}
+    >
+      {props.children}
+    </Link>
+  );
+
+  if (props.plain) {
+    return ret;
+  }
+  return <li>{ret}</li>;
+}