Update "CSS features reference"

[mikehoffms]

Rendered article sections for review:

• CSS features reference
  • /devtools/css/reference.md
  • Internal preview: https://review.learn.microsoft.com/microsoft-edge/devtools/css/reference?branch=pr-en-us-3771
  • External preview: https://github.com/MicrosoftDocs/edge-developer/blob/user/mikehoffms/css-ref/microsoft-edge/devtools/css/reference.md
  • Before/live: https://learn.microsoft.com/microsoft-edge/devtools/css/reference
  • Upstream: https://developer.chrome.com/docs/devtools/css/reference/
  • Revealed headings.
  • Updated local TOC.
  • Populated text in sections.
  • Populated pngs in sections.
  • todo: link to missing docs.

AB#60101398

[learn-build-service-prod]

Learn Build status updates of commit 1abdfd9:

💡 Validation status: suggestions

File	Status	Preview URL	Details
microsoft-edge/devtools/css/reference.md	💡Suggestion	View	Details

microsoft-edge/devtools/css/reference.md

• Line 303, Column 106: [Suggestion: other-site-link-broken - See documentation] Link 'https://developer.mozilla.org/docs/Web/CSS/--' points to a page that doesn't exist. Check the path or URL and update the link.

For more details, please refer to the build report.

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