ActionList: Add keyboard accessibility

[siddharthkp]

Part of https://github.com/github/primer/issues/447
Includes visual changes for keyboard focus from https://github.com/github/primer/issues/409

Please provide before/after screenshots for any visual changes

before:

tab.tab.fail.mov

after:

tabtab.mov

Merge checklist

• Added/updated tests
• NA Added/updated documentation
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

[changeset-bot]

🦋 Changeset detected

Latest commit: 5500790

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

This PR includes changesets to release 1 package

Name	Type
@primer/components	Patch

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[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	54.44 KB (0%)
dist/browser.umd.js	54.83 KB (0%)

[pksjce]

Hey not sure if this is valid. What does inset mean anyways?

Screen.Recording.2021-11-15.at.3.43.12.pm.mov

[siddharthkp]

Hey not sure if this is valid

The last option? Not sure how to adapt focus styles if the user has given custom styles to an Item with sx 🤔 Ideas? (happy to tackle in another PR)

What does inset mean anyways?

inset children are offset (vertically and horizontally) from List’s edges, full children are flush (vertically and horizontally) with List edges.