Support send/receive of videos

Naive approach, just downloading the whole chunk every time! Need to figure out caching and streaming for long-play stuff.

src/components/messages/MessageIncomingVideo.vue

@@ -0,0 +1,43 @@
+<template>
+  <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>
+    <div class="bubble image-bubble">
+      <v-responsive :aspect-ratio="16 / 9" :src="src">
+        <video :src="src" controls style="width:100%;height:100%">Video file</video>
+        <div v-if="downloadProgress" class="download-overlay">
+          <div class="text-center download-text">{{ downloadProgress }}% downloaded</div>
+        </div>
+      </v-responsive>
+      <QuickReactions :event="event" :reactions="reactions" />
+    </div>
+    <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";
+import attachmentMixin from "./attachmentMixin";
+
+export default {
+  mixins: [messageMixin, attachmentMixin],
+};
+</script>
+
+<style lang="scss">
+@import "@/assets/css/chat.scss";
+</style>