Add fade in-out between the images when navigate into the gallery

[prinkoID]

When navigate into the gallery with left and right the next/previous image is fast and create some glitch in some cases (probably only in mobile version)

[prinkoID]

It could be better a crossfade, or fade to a color, because now I'm seeing the website during the fade transition

[tobiasroeder]

This can be fixed by changing the background color from the ImageBox element in the CSS.

#imagebox {
  background-color: #000;
}