Improve rendering performance with content-visibility

[westonruter]

Feature Description

With the URL metrics gathered by Optimization Detective, it should be possible to automatically apply content-visibility to areas of the page to delay rendering them until they are in the viewport. This has the opportunity to improve INP.

See:

• https://web.dev/articles/content-visibility
• https://nitropack.io/blog/post/content-visibility-inp
• https://www.speedkit.com/blog/field-testing-css-containment-for-web-performance-optimization?s=03
• https://wordpress.slack.com/archives/C02KGN5K076/p1702577463610039