✨(video_player) lazy load embed video player

[igobranco]

Instead of loading the external video player, it only loads the video player if the user clicks on the big ▶ icon.

It only works on the published page. On the edit mode it still show the old behavior. This has performance benefits so the external video player JS libraries, like Youtube, only loads when the user wants to view the video.

The image that is uses is the video poster or the course cover.