DS Epic: Button Group

### **Description**

The Button Group component is a linear set of two or more buttons used to group related options. When a button in the group is selected, the selected state is visually highlighted. This can be used for some renderings of multi-select, as in a style for selecting multiple exposed items in a form or list, or as filters, outside the use of check boxes or dropdown lists.

No file, entry point, or test is named in the issue. Start by locating the design system's Button Group component area and review how existing components define selected states. Done should include a two-or-more-button group with a visually highlighted selected state, but the exact API, interactions, and acceptance tests still need clarification.

Written by the indexing model from the issue text.