Headerbar icons are transparent when their window is not focused, but otherwise share the same style as icons with selection. This updates the icon styles to match figma when selected.
* feat: add support for dark / light mode switching and simultaneouscustom light / dark mode themes
* refactor(color-picker): optional initial color and fallback color
* refactor: used FixedPortion for layout of the settings item
This makes sure that the control always has at least the specified portion of the available space
* refactor: make all members of the ThemeBuilder public
* refactor: add and update palette colors
* fix(theme): typo and derive PartialEq for ThemeBuilder
* fix: update color picker usage
* feat: add more variables to the theme
* fix: radius on headerbar
* fix: Theme CosmicConfigEntry impl
* chore: specify rev of taffy
* fix: theme CosmicConfigEntry missing variables
* fix: apply theme type when theme mode changes
* wip: add plus icon to empty color picker button
* chore: fix rev and imports
* refactor(color-picker): allow custom size for the icon
* refactor(color_picker): make color_button public
* update iced
