Resolve "No history message for new room members"

src/components/NoHistoryRoomWelcomeHeader.vue

@@ -0,0 +1,19 @@
+<template>
+  <div class="text-center">
+    <v-icon size="27" class="shield">$vuetify.icons.ic_security-shield</v-icon>
+    <div>{{ $t("room_welcome.no_past_messages") }}</div>
+  </div>
+</template>
+
+<script>
+export default {
+  name: "NoHistoryRoomWelcomeHeader",
+};
+</script>
+
+<style lang="scss">
+@import "@/assets/css/chat.scss";
+.shield {
+  margin-bottom: 12px;  
+}
+</style>