Use base classes for message types

This avoids unnecessary duplication of code for "avatar", "sender" etc in the general layout of messages.

src/components/messages/MessageIncoming.vue

@@ -0,0 +1,37 @@
+<template>
+  <!-- BASE CLASS FOR INCOMING MESSAGE -->
+  <div :class="messageClasses">
+    <v-avatar class="avatar" size="32" color="#ededed">
+      <img v-if="messageEventAvatar(event)" :src="messageEventAvatar(event)" />
+      <span v-else class="white--text headline">{{
+        messageEventDisplayName(event).substring(0, 1).toUpperCase()
+      }}</span>
+    </v-avatar>
+    <QuickReactions :event="event" :reactions="reactions" />
+    <!-- SLOT FOR CONTENT -->
+    <slot></slot>
+    <div class="op-button" ref="opbutton">
+      <v-btn icon @click.stop="showContextMenu($refs.opbutton)"
+        ><v-icon>more_vert</v-icon></v-btn
+      >
+    </div>
+    <div v-if="showSenderAndTime" class="senderAndTime">
+      <div class="sender">{{ messageEventDisplayName(event) }}</div>
+      <div class="time">
+        {{ formatTime(event.event.origin_server_ts) }}
+      </div>
+    </div>
+  </div>
+</template>
+
+<script>
+import messageMixin from "./messageMixin";
+
+export default {
+  mixins: [messageMixin],
+};
+</script>
+
+<style lang="scss">
+@import "@/assets/css/chat.scss";
+</style>