feat(playground): add submission layout component

src/app/(app)/playground/@problem/@submission/layout.tsx

@@ -0,0 +1,16 @@
+import ProblemSubmissionFooter from "./components/footer";
+
+interface ProblemSubmissionLayoutProps {
+  children: React.ReactNode;
+}
+
+export default function ProblemSubmissionLayout({
+  children,
+}: ProblemSubmissionLayoutProps) {
+  return (
+    <div className="h-full flex flex-col">
+      <div className="flex-1">{children}</div>
+      <ProblemSubmissionFooter />
+    </div>
+  );
+}