Auto Item Spacing

## Problem

When items spacing for auto layout is set to auto, it is unclear how to represent item spacing in the spec. This is related to the primary axis aligned items property

[primaryAxisAlignItems](https://developers.figma.com/docs/plugins/api/properties/nodes-primaryaxisalignitems/): 'MIN' | 'MAX' | 'CENTER' | 'SPACE_BETWEEN'