SplitViewController, ColorWell, TabView, Button

• Added .introspectSplitViewController() on iOS
• Fixed iPad tests
• Added iPad to CI
• Added .introspectColorWell() on iOS and macOS
• Added .introspectButton() on macOS
• Fix UITextField with cornerRadius
• Added .introspectTabView() on macOS

Thanks to @SplittyDev and @JannThomas from Quintschaf for maintaining the project!