Get visible elements currently in viewport without groupCells

Hi @desandro ,

don't know if it is supported in some way, but I wanted to ask help with a issue I'm trying to solve:

I have a carousel with multiple visible elements and wanted to **get the current visible elements**. in the flickity-viewport.

I can achieve this using **groupCells** and using the **.is-selected** class attached to the element in the group.

the problem is that I need the slider to move by one element at a time, and not, for example, in steps of 3 elements using the **groupCells** option.

**Test case:** https://codepen.io/anon/pen/oGLjqy

is there a way to do it in a simple way using your plugin's tools or have I to integrate it with something else?

Start with the linked CodePen test case and inspect Flickity's existing plugin tools for how selected or visible carousel elements are represented. The desired result is to identify the elements currently visible in the viewport while advancing one element at a time without using groupCells.

Written by the indexing model from the issue text.