Ability for Transitioner to navigate (without transitions) when app is not active (in focus).

Is your feature request related to a problem? Please describe.
I would like to be able to have a transition between pages of my application that are triggered in code after a potentially long running task.
If I run my demo application and click on the Next or Back buttons and then activate another window (e.g. Visual Studio) while the background delay is being awaited, when the process completes no Transition occurs.
However, if the demo app remains the active window it transitions as expected.

Describe the solution you'd like
For the page navigation to happen, ideally with transitions if the windows is visible.
If the window is not visible then page navigation should occur, but maybe without any transitions (instant change to control z-order)

Describe alternatives you've considered
Not sure of any other alternatives other than rolling my own Navigation functionality.

Additional context
My simplified demo app can be found in my Izzy-Transitioner-Demo branch of my fork (see: https://github.com/thepinkmile/MaterialDesignInXamlToolkit/tree/Izzy-Transitioner-Demo)

从 issue 中描述的 Transitioner 行为开始，使用链接的 Izzy-Transitioner-Demo 分支复现该行为，并比较活动窗口和非活动窗口。跟踪由 Next/Back 触发的导航，并将 done 定义为在窗口处于非活动状态时导航完成；如果支持，则在窗口可见时保留 transitions。