Autoplay gif/videos thumbnails

[n1c0saurio]

Like on the web, basically.

[Vistaus]

Fine with me, but only if it becomes optional 'cause I hate it when stuff autoplays. And by optional I mean that either autoplay should be off by default but with a setting to enable it or on by default but with a setting to disable it (a setting in either the settings or dconf-editor).