feat(accordion): add css custom properties

[yuhsianw]

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)
• [ ] If applicable, have a visual design approval

PR Type

What kind of change does this PR introduce?

• [ ] Bugfix
• [x] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Documentation content changes
• [ ] clarity.design website / infrastructure changes
• [ ] Other... Please describe:

What is the current behavior?

Issue Number: https://github.com/vmware-clarity/core/issues/278

What is the new behavior?

--box-shadow, --icon-visibility, and --icon-margin CSS custom properties added to cds-accordion-header.

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Other information

[vmwclabot]

@yuhsianw, you must sign our contributor license agreement before your changes are merged. Click here to sign the agreement. If you are a VMware employee, read this for further instruction.

[github-actions[bot]]

👋 @yuhsianw,

• 🙏 The Clarity team thanks you for opening a pull request
• ⏳ The build for this PR has started
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Thank you,

🤖 Clarity Release Bot

[vmwclabot]

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[vmwclabot]

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[yuhsianw]

Closing PR following https://cla.vmware.com/employee

[github-actions[bot]]

Hi there 👋, this is an automated message. To help Clarity keep track of discussions, we automatically lock closed PRs after 14 days. Please look for another open issue or open a new issue with updated details and reference this one as necessary.