feat: add <sd-checkbox /> and <sd-checkboxgroup />

[GeekyEggo]

• Adds <sd-checkbox />.
• Adds <sd-checkboxgroup />.
• Fixes incorrect activation space around <sd-switch />.
• Updates <sd-switch /> to be read from textContent, rather than label.
• Updates <sd-switch /> styles to align with <sd-checkbox />.
• Removes <sd-label /> from <sd-switch />.

[ChekTek]

It looks like in a <sd-radiogroup> the label or the slot content from the inner <sd-option> is displayed, but in a <sd-checkboxgroup> only slot content from the inner <sd-option> is displayed. I think we should also be looking for the label property of the <sd-option> here?

<sd-field label="Radio Group">
	<sd-radiogroup setting="radioSetting">
		<sd-option label="Value 1" value="1">Other Value</sd-option>
		<sd-option label="Value 2" value="2"></sd-option>
		<sd-option label="Value 3" value="3"></sd-option>
	</sd-radiogroup>
</sd-field>
<sd-field label="Checkbox Group">
	<sd-checkboxgroup setting="checkboxGroupSetting">
		<sd-option label="Value 1" value="1">Other Value</sd-option>
		<sd-option label="Value 2" value="2"></sd-option>
		<sd-option label="Value 3" value="3"></sd-option>
	</sd-checkboxgroup>
</sd-field>

[GeekyEggo]

Great call out; I've updated the following option-type elements to utilize their textContent as the label:

• <sd-checkbox />
• <sd-option />
• <sd-radio />
• <sd-switch />

This allows for the elements to be constructed in a similar manor to <select />, for example

<sd-switch setting="isOn">On / Off</sd-switch>

Or in the context of a group:

<sd-checkboxgroup setting="options">
    <sd-option value="1">One</sd-option>
    <sd-option value="2">Two</sd-option>
</sd-checkboxgroup>