Sustainability chapter should be in the User Experience section, not Content Publishing

[ldevernay]

Sustainability directly benefits to user experience through optimising user journeys, allowing usage with low or no bandwidth and promoting accessibility, seo and privacy (and directly improving performance through efficiency and sobriety). Also, it is not limited to content publishing but also web (and other) applications. Some of the main topics of sustainability are sticking to the essential, for instance by avoiding deceptive patterns and removing irrelevant content (thus reducing the cognitive load for users).