TJSW: clarify reasoning behind controlled order of properties

As of ES2020 object keys iteration order follows definition order in nearly all (if not all) methods of iteration thorough object properties.
Actual goal: order of properties must be controlled when it is important. We need to handle situations when definition order is not controlled at source (e.g. API responses, new literals do not follow implicit convention).

No file, test, or entry point is identified in the issue. Begin by locating the material that discusses controlled object-property order, then define the explanation and examples needed to cover API responses and literals whose definition order is not controlled; done when that rationale is clear to learners.

Written by the indexing model from the issue text.