feat: Enable custom on click handler passed via accordion item

[kleinschmidtj]

Summary

Users pass in items to the Accordion component and those items could have custom onClick handlers that fire via the handleToggle prop. (For example, custom GA tracking events described in the below issue.) This change actually implements firing those passed-in functions.

Related Issues or PRs

addresses #2739

How To Test

In Accordion.stories.tsx, add a line to the first item in the testItems array:

    handleToggle: () => {
      console.log('hello')
    },

Open one of the Accordion stories in Storybook, open the developer console, click the first Accordion item and you should see "hello" appear.

Screenshots (optional)

[github-actions]

	Warnings
⚠️	This PR does not include changes to storybook, even though it affects component code.

Generated by 🚫 dangerJS against d1d9ae6

[brandonlenz]

LGTM! Thanks for wiring this up!