Scene player improvements (#3020)

* Add types to player plugins
* Use videojs-vtt.js to parse sprite VTT files
* Overhaul scene player
* Replace vtt-thumbnails-freetube
* Remove chapters_vtt
* Force remove shadow from player progress bar
* Cleanup player css
* Rewrite live.ts as middleware
* Don't force play when changing source

ui/v2.5/src/components/ScenePlayer/util.ts

@@ -1,6 +1,6 @@
-import VideoJS from "video.js";
+import videojs from "video.js";
 
 export const VIDEO_PLAYER_ID = "VideoJsPlayer";
 
 export const getPlayerPosition = () =>
-  VideoJS.getPlayer(VIDEO_PLAYER_ID).currentTime();
+  videojs.getPlayer(VIDEO_PLAYER_ID).currentTime();