Provide a way to roll over GIFs when input device is not hover-capable

[IvanSanchez]

Related to #2416: there are use cases (tablets) where the pointer input device used has no capability to 'hover' over an element (should be able to be checked using the InputDeviceCapabilities interface). Provide a button or something to play/stop the animation, even for hover-capable input devices.

[uhoreg]

FWIW, clicking on the image will display it in a lightbox and play the animation. Though it would be good to have a visible control to play gifs in the timeline too.

[t3chguy]

InputDeviceCapabilities is still non-standard so we cannot use it, namely Firefox & Safari do not support it