prismTestSizes top-level constant
Sizes worth testing any adaptive component at.
These are not arbitrary: phone is the narrowest layout most apps support,
tablet straddles the compact/medium boundary, and desktop is where
two-pane layouts and extended navigation rails appear.
Implementation
const prismTestSizes = <String, Size>{
'phone': Size(320, 568),
'tablet': Size(834, 1112),
'desktop': Size(1440, 900),
};