Function switchTab

switchTab(
    state: MobileNavigationState | undefined,
    screen: MobileScreen,
    step: NavigationStep,
): MobileNavigationState
A bottom-tab switch: the chain restarts at the tab root (outside a chain only the front screen changes).
Parameters
- state: MobileNavigationState | undefined
- screen: MobileScreen
- step: NavigationStep
Returns MobileNavigationState