Autoplay embedded videos after the play button is clicked

Summary

Currently embedded videos need to have the play button clicked twice. First to remove the cover (and allow sending user data to the remote server). Second because the iframe embed often includes its own play button and does not autoplay by default.

This change will try to make the embed autoplay, so you don't have to click the Play button twice.

Screenshots (if appropriate):

Before	After
Kazam_screencast_00050	Kazam_screencast_00052