Issue #3376312 by pdureau: Add Dark mode with UI Skins

ui_suite_protocol.info.yml

@@ -9,6 +9,7 @@ dependencies:
   - ui_patterns:ui_patterns_library
   - ui_patterns_settings:ui_patterns_settings
   - ui_styles:ui_styles
+  - ui_skins:ui_skins
 libraries:
   - ui_suite_protocol/base
   - ui_suite_protocol/preview

ui_suite_protocol.ui_skins.themes.yml

+dark:
+  label: "Dark"
+  description: Applies a dark background color with light foreground colors.
+  value: mzp-t-dark