[Glitch] Fix new audio player features not working on Safari

Port 51b5bb5301 to glitch-soc

Signed-off-by: Thibaut Girka <thib@sitedethib.com>

app/javascript/flavours/glitch/features/audio/index.js

@@ -254,6 +254,7 @@ class Audio extends React.PureComponent {
   }
 
   _initAudioContext () {
+    const AudioContext = window.AudioContext || window.webkitAudioContext;
     const context      = new AudioContext();
     const source       = context.createMediaElementSource(this.audio);