Add play button to video custom controls

If autoplay is not working on browser, user can play the video with this button

static/galene.css

@@ -568,6 +568,10 @@ textarea.form-reply {
     text-align: center;
 }
 
+.video-controls .video-play {
+    font-size: 0.85em;
+}
+
 .video-controls span.disabled, .video-controls span.disabled:hover, .top-video-controls span.disabled:hover{
     opacity: .2;
     color: #c8c8c8

static/galene.html

@@ -231,6 +231,9 @@
     <div id="videocontrols-template" class="invisible">
       <div class="video-controls vc-overlay">
         <div class="controls-button controls-left">
+          <span class="video-play" title="Play video">
+            <i class="fas fa-play"></i>
+          </span>
           <span class="volume" title="Volume">
             <i class="fas fa-volume-up volume-mute" aria-hidden="true"></i>
             <input class="volume-slider" type="range" max="100" value="100" min="0" step="5" >

static/galene.js

@@ -1166,6 +1166,14 @@ function setVolumeButton(button, muted) {
  * @param {HTMLElement} container
  */
 function registerControlHandlers(media, container) {
+    let play = getVideoButton(container, 'video-play');
+    if(play) {
+        play.onclick = function(event) {
+            event.preventDefault();
+            media.play();
+        };
+    }
+
     let volume = getVideoButton(container, 'volume');
     if (volume) {
         volume.onclick = function(event) {