FAQ a11y sign off updates

[JoshBowdenConcepts]

Summary

A number of a11y changes to ensure full accessibility for the FAQ component.

List of notable changes:

• added FAQ.Group to the FAQ component to provide accessible markup
• updated Accordion summary spacing so that the focus would not obscure the text

What should reviewers focus on?

• Making sure each of the items within this issue are addressed.

Steps to test:

1. Open the FAQ component in CI-deployed preview environment
2. Go to FAQ story in Storybook
3. Verify that # behaves as described in the following issue.

Supporting resources (related issues, external links, etc):

• closes https://github.com/github/primer/issues/1675

Contributor checklist:

• [ ] All new and existing CI checks pass
• [ ] Tests prove that the feature works and covers both happy and unhappy paths
• [ ] Any drop in coverage, breaking changes or regressions have been documented above
• [ ] New visual snapshots have been generated / updated for any UI changes
• [ ] All developer debugging and non-functional logging has been removed
• [ ] Related issues have been referenced in the PR description

Reviewer checklist:

• [ ] Check that pull request and proposed changes adhere to our contribution guidelines and code of conduct
• [ ] Check that tests prove the feature works and covers both happy and unhappy paths
• [ ] Check that there aren't other open Pull Requests for the same update/change

Screenshots:

The spacing here between the heading and content is increased to allow for the focus border to not block the details text

Before	After