Add piped support

- add playerInit listener
- made popup container generic for possible piped support
- explicitly add css files to web_accessible_resources

src/utils/pageUtils.ts

@@ -9,6 +9,8 @@ export function getControls(): HTMLElement {
         ".player-controls-top",
         // Invidious/videojs video element's controls element
         ".vjs-control-bar",
+        // Piped shaka player
+        ".shaka-bottom-controls"
     ];
 
     for (const controlsSelector of controlsSelectors) {