Component for grouping and organizing list items with collapsible structure.

ListGroup is an auxiliary component for List, managing hierarchical content organization with expand/collapse functionality. The component integrates with MotionTransform for smooth animations, supports unlimited nesting levels, and provides convenient navigation through structured data.

**Key features:**

- Hierarchical content organization with unlimited nesting
- Expand/collapse animations via MotionTransform
- State management via props or internal state
- Automatic group content visibility control
- Integration with List component ecosystem
- Customization support via head and list slots
- Group state change events

**Common use cases:**

- Grouping list items by categories
- Creating tree-like navigation structures
- Organizing settings and options by sections
- Multi-level menus and catalogs
- FAQ sections with expandable answers

```html
<script setup>
import { ref } from 'vue'

const items = [
  { text: 'Item 1', value: '1' },
  { text: 'Item 2', value: '2' },
  { text: 'Item 3', value: '3' }
]

const isOpen = ref(true)
</script>

<template>
  <List>
    <ListGroup v-model:open="isOpen">
      <template #head="{ open }">
        <div class="group-header">
          <span>{{ open ? '▼' : '▶' }}</span>
          <span>Group Items</span>
        </div>
      </template>

      <template #list>
        <ListItem
          v-for="item in items"
          :key="item.value"
          :text="item.text"
        />
      </template>
    </ListGroup>
  </List>
</template>
```
