docs(angular): add transitions & triggers content (#6562)

src/data/roadmaps/angular/content/transitions--triggers@Iv2d4sgODqMPzA9gH6RAw.md

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-# Transitions & Triggers
+# Transitions & Triggers
+
+In Angular, transition states can be defined explicitly through the `state()` function, or using the predefined `*` wildcard and `void` states. An asterisk `*` or wildcard matches any animation state. This is useful for defining transitions that apply regardless of the HTML element's start or end state. Use the `void` state to configure transitions for an element that is entering or leaving a page.
+
+Visit the following resources to learn more:
+
+- [@official@Angular Official Docs - Transition and Triggers](https://angular.dev/guide/animations/transition-and-triggers)
+- [@video@Angular Animations: Learn the basics](https://www.youtube.com/watch?v=CGBcIz1tYec)
+- [@video@How to use trigger function in Angular Animations](https://www.youtube.com/watch?v=3_B4OV5M_Ag)