feat: "peek" view of slides on hover

[patrickkmatias]

after hovering a slide for some seconds with some visual feedback of these seconds, it would display in bigger picture.

If the mouse moves in the bigger picture mode, it would deactivate (disappear); if the spacebar is being pressed, even moving the mouse wouldn't deactivate the peek view mode.

[patrickkmatias]

it also

• [ ] should have a button that when pressed while viewing would preview it with the actual presenting screen aspect ratio