Support video trailers

[MrEliptik]

When showcasing games, it could be cool to have trailers running when the launcher is not in use. It could be added next to the description or play in full screen. If in full screen, the video would stop as soon as the game detects any input. It could be launched automatically after X seconds of inactivity. Either launch all trailers one after the other or launch only the trailer corresponding to the selected game.

[MrEliptik]

I decided to add a button to launch the trailer instead of having it automatically start.