refactor(assetlist)!: migrate to spectrum tokens

[jenndiaz]

Description

Migrates AssetList to spectrum tokens

• addresses empty label a11y issue (on docs site, storybook, and within Miller Column)
• Adds is-navigated AssetList-Item to docs site
• Adds WCHM values
• Addresses previous issue with text color on dark and darkest and focus indicators

How and where has this been tested?

Please tag yourself on the tests you've marked complete to confirm the tests have been run by someone other than the author.

Test Outline:

@jawinn

1. Open the docs site for the asset list component:

• there is a 4th asset item, Downloads with is-navigated styling
• Tabbing through there is a focus indicator
• component contrast is appropriate for all color themes (light, dark, darkest)
• a11y testing has an accessible name for each check box

2. Open the storybook for the asset list component:

• there are no a11y violations
• Hover, selected, and navigated all match docs site

Regression testing

Validate:

1. A legacy documentation page (such as accordion), including:

• The page renders correctly
• The page is accessible
• The page is responsive

4. A migrated documentation page (such as action group), including:

• The page renders correctly
• The page is accessible
• The page is responsive

Screenshots

To-do list

• I have read the contribution guidelines.

• I have updated relevant storybook stories and templates.

• I have tested these changes in Windows High Contrast mode.

• If my change impacts other components, I have tested to make sure they don't break.

• If my change impacts documentation, I have updated the documentation accordingly.

• ✨ This pull request is ready to merge. ✨

[github-actions]

🚀 Deployed on https://pr-2211--spectrum-css.netlify.app

[jawinn]

Nice work with this, including the accessibility fixes! I've confirmed the validation steps and everything looks right, and improved.

I don't think --spectrum-assetlist-checkbox-margin is used, so that can probably be removed?

My only suggestion would be to pass an id into the Checkbox story in Storybook, as Chrome console shows a recommendation about it not having an id or name (while also saying it's not strictly necessary)---the docs examples do already have an ID on them, so that would help align the markup.

[pfulton]

Definitely an improvement on dark and darkest which look broken in production...

Thanks for taking care of this!