GA: entered livestream (#364)

## Issue
85: "user joined livestream"

## Approach
Add it into the existing "player :: action" event, so we can compare it againts `loaded_video | loaded_image | loaded_markdown | loaded_audio`.

ui/analytics.js

@@ -383,6 +383,8 @@ const analytics: Analytics = {
           return 'loaded_markdown';
         case RENDER_MODES.IMAGE:
           return 'loaded_image';
+        case 'livestream':
+          return 'loaded_livestream';
         default:
           return 'loaded_misc';
       }

ui/page/livestream/view.jsx

@@ -23,6 +23,11 @@ export default function LivestreamPage(props: Props) {
   const [isLive, setIsLive] = React.useState('pending');
   const livestreamChannelId = channelClaim && channelClaim.signing_channel && channelClaim.signing_channel.claim_id;
 
+  React.useEffect(() => {
+    // TODO: This should not be needed one we unify the livestream player (?)
+    analytics.playerLoadedEvent('livestream', false);
+  }, []);
+
   React.useEffect(() => {
     if (!livestreamChannelId) {
       setIsLive(false);