Method to start projection

[dramcio]

Is your feature request related to a problem? Please describe.
Issue occurs when you have a few pages in PageView.
You add BubbleShowcase to the third page.
So if you open this widget with PageView you are actually on the first page.

Go to the third page, BubbleShowcase started before the end of the animation (animations when you move from first to third page)

So, it does not properly highlight widgets (it highlights widget out of the screen and so on)

Describe the solution you'd like
We should have a possibility to start animations manually. Like in showcaseview.

WidgetsBinding.instance.addPostFrameCallback((_) =>
        ShowCaseWidget.startShowCase(context, [_one, _two, _three]));

Describe alternatives you've considered
The default behaviour of starting BubbleShowcase projections should wait until the UI build is completely finished.

Additional context
Add any other context or screenshots about the feature request here.