Allow setting the initial state of the AnimationTextController

**Is your feature request related to a problem? Please describe.**
I would like chain some of the Animations.

**Describe the solution you'd like**
To allow this, it should be enough to set the initial AnimatedTextState in AnimatedTextController()
EDIT: The AnimatedText should also not override this value.
change
```dart
// in _initAnimation()

_animatedTextController.state = AnimatedTextState.playing; // remove
_controller.forward();
```
to
```dart
// in _initAnimation()

// _animatedTextController.state = AnimatedTextState.playing;
if (_animatedTextController.state == AnimatedTextState.playing) _controller.forward();
```

**Additional context**
I have a title and a subtitle where the title should start animating instantly, while the subtitle starts after that.
Both should than stay on screen.

Something like:
Title: "Welcome to my App"
Subtitle: "Before we start, we have a few questions for you"