Add E2EE banner

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/Banner.tsx

@@ -0,0 +1,27 @@
+/*
+Copyright 2023 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { ReactNode } from "react";
+
+import styles from "./Banner.module.css";
+
+interface Props {
+  children: ReactNode;
+}
+
+export const Banner = ({ children }: Props) => {
+  return <div className={styles.banner}>{children}</div>;
+};