Checkbox group: cannot preselect more than one option

[alina-lapina]

Describe the bug
Cannot (pre)select more that one option.

To Reproduce
Steps to reproduce the behavior:

<CheckboxGroup
	header="Header"
	onChange={() => callback}
	orientation="column"
	selectedValue="item2"
	items={[
		{ label: 'Checkbox 1', value: 'checkbox1' },
		{ label: 'Checkbox 2', value: 'checkbox2' },
		{ label: 'Checkbox 3', value: 'checkbox3', disabled: true },
	]}
/>

Expected behavior
It should be possible to preselect several options, because checkbox is meant to be collectively exhaustive, while input type=radio is mutually exclusive.
Each item in the group has to be responsible for its selection in the group: { label: '...', value: '...', selected: true/false },

<CheckboxGroup
	header="Header"
	onChange={() => callback}
	orientation="column"
	items={[
		{ label: 'Checkbox 1', value: 'checkbox1' },
		{ label: 'Checkbox 2', value: 'checkbox2', selected: true },
		{ label: 'Checkbox 3', value: 'checkbox3', disabled: true },
	]}
/>

[ssb-cgn]

Har opprettet en sak på dette hos oss nå :)