Add Checkbox and CheckboxGroup components

[mkernohanbc]

This PR adds two new components, and their supporting documentation:

• Checkbox
• CheckboxGroup

They are based on RAC Checkbox and CheckboxGroup.

Checkbox renders a focusable/selectable <div> and a hidden <input>. The text label is set via the children slot:

Checkbox supports the following states:

• required
• disabled
• read-only
• indeterminate

Note: Checkbox can be used independently of a CheckboxGroup, but using it as a standalone component requires additional work to add validation and error handling that CheckboxGroup has built-in.

CheckboxGroup provides a semantic wrapper for one or more checkboxes:

It includes these slots:

• children (expects an array of Checkbox components)
• label
• description
• errorMessage (via FieldError)

Additionally, the orientation prop can be used to toggle the layout of a group between vertical (default) and horizontal.

[ty2k]

I've made changes to the Checkbox and CheckboxGroup to bring in our latest changes, update the styles to match our most up to date design, and add tests. With these changes, I think we're ready to merge. Will mark this as approved and leave it up to you to confirm, @mkernohanbc.

• Functional updates
  • flexWrap prop added to CheckboxGroup to allow wrapping horizontal options rather than overflowing caf74a5, eb24ea6
  • Custom TypeScript interface removed from Checkbox in favor of just using the RAC defaults (no difference in how the component is used, just cleaner this way) 9cb5205
  • children removed from interface in CheckboxGroup in favor of the RAC default (no difference in use) 4976771
• Style updates
  • Cursor styles are applicable for the entire checkbox + label, not just the box itself a9bfa01
  • Disabled checkbox label gets disabled font color 9a036ab
  • Add styles for isIndeterminate + isDisabled dd65760
  • Add styles for isIndeterminate + isInvalid 01f9f22
  • Checkbox flex gap changed to 10px to match current design 6206192
  • Checkbox border styles updated to match current design (border color matches background color in most filled states) 8073da6
• Tests
  • Checkbox d103d15, 9d26371
  • CheckboxGroup bd6f5ce, 400cd6c
• Storybook updates
  • Add isInvalid and isSelected props to Checkbox template b4d9797
• Merge latest from main afce1ce

isIndeterminate + isDisabled:

isIndeterminate + isInvalid:

flexWrap defaulted to nowrap:

flexWrap set to wrap:

[mkernohanbc]

Thanks for all your work to clean this up @ty2k — looks good to me! Will squash and merge now.