Accordion - update examples to show two html variations

[jgiardino]

Here are a few examples of accordions out there:
https://www.w3.org/TR/wai-aria-practices-1.1/#accordion
https://inclusive-components.design/collapsible-sections/
https://www.scottohara.me/blog/2017/10/25/accordion-release.html
https://a11yproject.com/patterns/

The first 3 use headings, without a definition list. The last link includes an example, "Simple Accordion", that uses a definition list and not headings.

Our pattern uses both, which isn't considered valid html. Instead, we should support one or the other. Our core css currently supports not including a heading, but it doesn't support not using the <dl> elements.

Updates needed for this issue:

• Update the examples shown to use either headings or definition list
• Include an extra example showing the other variation
• Make sure the css gets applied to both variations as expected
• Create an issue in react to make similar updates when this issue closes

[patternfly-build]

🎉 This issue has been resolved in version 2.16.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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