docs(css): Update contain keyword in ray() and add other edits

[dipikabh]

Description

This PR tweaks the contain keyword description on the ray() page to match the spec.

Also:

• Fixes a link to the offset-anchor property
• Edits example result description for better clarity

Motivation

There is implementation adjustment for the contain keyword in ray() function.

• Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1821450
  (contains the link to the chromium patch for this update: https://chromium-review.googlesource.com/c/chromium/src/+/4453583)
• Spec: https://drafts.fxtf.org/motion/#valdef-ray-contain

Additional details

In Firefox, ray() is available behind the flag layout.css.motion-path-ray.enabled that needs to be enabled.

Related issues and pull requests

FX115 doc issue tracker: #27178

For reference: PR that added the ray() function documentation

[github-actions]

Preview URLs

• /en-US/docs/Web/CSS/ray

(comment last updated: 2023-06-23 13:50:10)

[dipikabh]

Thank you for the review, @estelle!