v2.15.2

Fixed

• color.gradient is emitted (#398). GlobalStylesEmitter now writes color.gradient as background at the root, on elements and their states, and on blocks. It comes before background-color, so a node with both keeps its color, as WordPress does. Before, the value was dropped. visual-editor's canvas stylesheet uses only this emitter, so a theme's gradient buttons and sections rendered without their gradient in the Site Editor while the front end showed it. The emitter cache key moves to v11, so cached CSS is rebuilt on deploy.