fix(FEC-12539): Shaka text displayer font size too small on TVs - Reg…

…ression (#210)

solves: FEC-12539 - Regression 

**issue:** the previous fix is incorrect since the media query refers to the screen size and not the player size

**fix:** The :fullscreen [CSS](https://developer.mozilla.org/en-US/docs/Web/CSS) [pseudo-class](https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-classes) is not applied in samrtTvs, so instead i relying on the Env.IsSmartTv env variable

src/dash-adapter.js

@@ -412,7 +412,9 @@ export default class DashAdapter extends BaseMediaSourceAdapter {
     if (this._config.useShakaTextTrackDisplay) {
       this._shaka.setVideoContainer(Utils.Dom.getElementBySelector('.playkit-subtitles'));
       if (Env.isSmartTV) {
-        document.querySelector('.shaka-text-container').style.fontsize = '4.4vmin';
+        this._eventManager.listenOnce(this._videoElement, EventType.DURATION_CHANGE, () => {
+          document.querySelector('.shaka-text-container').style.fontSize = '4.4vmin';
+        });
       }
     }
   }