Support for small screens

[elondaits]

When using the Snapshot Slider on a small screen there are just a few things that are impractically small:

• The print / email icons are too tiny to click. They could have the size defined using viewport/dependent size units (vmin, vmax, vh, vw).
• The QR code is too small It could grow (a-la lightbox) when clicked.

[porst17]

The overall layout of the slider is pretty static and it is quite hard to change that since it has a lot of side effects.

I could imagine the following: When someone clicks on the button bar (which is the part below the vertical slider) and doesn't hit one of the buttons, the button bar could just grow to a reasonable size and with it the buttons and the QR code.

The buttons are symbols from a font and the QR code is generated as SVG IIRC. So this should not be an issue. We still need to figure out how the resized bar should look like exactly.

[elondaits]

If there's a need to install a snapshot slider on a small screen in the future (it worked quite well in that size) I can try to add some responsive behavior to make the button bar bigger and fight the layout until only one of us remains.