feat: add ChipSelectChip

[kurtdoherty]

This PR

• Part 1 of v5 component refactor: Chip Select #424
• Adds new ChipSelectChip component. This is effectively a styled checkbox. When more than one are used together with the same name and in the same form, they work as a checkbox group.
• The chip has built-in handling for single-selection, though this only works when the checked state of the chips is uncontrolled. As soon as the checked state is controlled, the consumer bears the burden of ensuring the single-selection behaviour works when required. A future PR will add a helper function for consumers to use that will take care of most of this concern.

note: checkbox inputs were used over radio button because it was non-trivial to implement the required toggling functionality (clicking a chip will check OR uncheck it) on top of radio buttons. This is because radio buttons are not designed to be unchecked when clicked on. Further, radio button groups include special keyboard navigation handling that causes the checked radio to change as the options are navigated using arrow keys; this would only be appropriate in the single-selection context of the chip select. In the end, checkboxes seemed the better fit, with single-selection behaviour being the only "custom" behaviour we need to model.

[rpt-uk-github]

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	Coverable lines	Covered lines	Coverage
Common ancestor commit (e0c2a49)	Report Missing	Report Missing	Report Missing
Head commit (19749fc)	9131	8443	92.47%

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Pull request (#757)	51	51	100.00%

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