feat(combobox): make the title collapsible

[YiyangLi]

Hi, I want to add a feature to combox, specifically making the group label collapsible. We are not able to use groupLabelTemplate to simply add an interactive button. Because we are not able to "hide" the children items under the group.

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🦋 Changeset detected

Latest commit: 736804b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@twilio-paste/combobox	Major
@twilio-paste/core	Patch
@twilio-paste/website	Patch

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[YiyangLi]

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@twilio-paste/token-contrast-checker	Configuration

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[nkrantz]

Update: after speaking with the team and with @YiyangLi we've decided to close this PR for now. DSYS doesn't have the capacity to facilitate non-roadmap contributions at the moment, but we'll reassess this contribution when we have more capacity.