Support `gap` containers

[Bilge]

Is your feature request related to a problem? Please describe.
When Shuffle kicks in, the gap is lost.

Describe the solution you'd like
Gap is respected.

Describe alternatives you've considered
Applying margin is not always possible in certain designs.

Additional context

gap.mp4

[glen-cheney]

What's preventing you from using the gutterWidth option?

When it's a function, it takes precedence over the sizer's marginLeft:

Shuffle/packages/shuffle/src/shuffle.js

Lines 390 to 396 in edbee18

	if (typeof this.options.gutterWidth === 'function') {
	size = this.options.gutterWidth(containerWidth);
	} else if (this.options.sizer) {
	size = getNumberStyle(this.options.sizer, 'marginLeft');
	} else {
	size = this.options.gutterWidth;
	}

[Bilge]

I guess that would be fine, even if it would be nicer to detect the CSS gap.