Add test code examples for Vue component including `Transition`

Hi there ✋ This pull request adds specific test code examples for a Vue component that includes the [`Transition`](https://vuejs.org/guide/built-ins/transition.html) built-in component. I implemented a Vue component including the `Transition` using [JavaScript Hooks](https://vuejs.org/guide/built-ins/transition.html#javascript-hooks), and I needed to implement test code for my component. I also wanted to know test code examples for such components, but I couldn't find any in [the test code directory](https://github.com/testing-library/vue-testing-library/tree/main/src/__tests__), so I added them.