Usage
ItemGroup replaces ui-core ListGroup (CORE-979). It is the ul host for Item rows. Menu and Select wrap their options in ItemGroup and Item.
The host is a flex column with a --space-4 row gap (ITG-1). style is excluded (ITG-2). The list has no markers, margin, or padding. The host gets role="list" unless you pass another role, because WebKit exposes a list without markers as a group.
itemGroup.itemOne and itemGroup.itemTwo.