Timeout on room deletion

And custom deletion notice state event.

Issue #118.

src/components/messages/RoomDeletionNotice.vue

@@ -0,0 +1,23 @@
+<template>
+  <!-- ROOM WILL BE DELETED -->
+  <div class="notice">
+    👋&nbsp;
+    {{
+      $t("purge_room.room_deletion_notice", {
+        user: stateEventDisplayName(event),
+      })
+    }}
+  </div>
+</template>
+
+<script>
+import messageMixin from "./messageMixin";
+
+export default {
+  mixins: [messageMixin],
+};
+</script>
+
+<style lang="scss">
+@import "@/assets/css/chat.scss";
+</style>