docs: make player container overflow hidden due to mux-video weirdness.

examples/nextjs-with-typescript/src/app/material-ui-player-chrome/components/PlayerContainer.tsx

@@ -26,6 +26,7 @@ const PlayerContainer = ({ children }: { children: ReactNode }) => {
         backgroundColor: 'black',
         width: '80vw',
         aspectRatio: '16/9',
+        overflow: 'hidden',
       }}
     >
       {children}