v0.8.0-beta.3

• adds childPosition to ActionSlider.standard
• adds childAnimation parameter to ActionSlider.standard and ActionSlider.dual
• migrates from SliderMode to SliderStatus
• adds status to all constructors
• adds expanded, highlighted and side parameters to SliderMode.loading, SliderMode.success
  and SliderMode.failure
• BREAKING: renames customForegroundBuilder to customIconBuilder
• BREAKING: changes default background color from ThemeData.cardColor to ThemeData.colorScheme.surface
• BREAKING: removes rolling in favor of the new iconAnimation parameter
• BREAKING: renames SlidingState to SlidingStatus
• BREAKING: moves parameters in ActionSlider.standard and ActionSlider.dual to style:
  • backgroundColor
  • backgroundBorderRadius (renamed to borderRadius)
  • toggleColor
  • boxShadow
• adds option to add SliderStyle to extensions of ThemeData