Add Flex box support to groups

When you have items in a group in XD they are currently absolutely positioned. Adding Flex box support allows you to tell the browser to layout of the elements dynamically.

Flex box supports horizontal alignment and vertical alignment, spacing and distributing.

Combining this with multiple query support allows you to change an elements layout properties as a page size changes.

This feature is added. Go to group layout and select row, column or stack. Then set the flex box options.