Connection lost banner (#1101)

* connection lost banner
if there is no connection to the home server

Signed-off-by: Timo K <toger5@hotmail.de>

src/DisconnectedBanner.module.css

@@ -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.
+*/
+
+.banner {
+  position: absolute;
+  padding: 29px;
+  background-color: var(--quaternary-content);
+  vertical-align: middle;
+  font-size: var(--font-size-body);
+  text-align: center;
+  z-index: 1;
+  top: 76px;
+  width: calc(100% - 58px);
+}