Lazy-loading design images with IntersectionObserver

What does this MR do?

Previously, all design images were loaded on the initial page load. With IntersectionObserver, only those designs that are in view, load their images with a given link. This allows us to download images one-by-one, reducing an initial page load time, initial page weight, and system resource usage.

Screenshots

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Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done