Support for JUnit 5

Hi

is there any plan to provide something similar to the `GUITestRunner` and `AssertJSwingJUnitTestCase` for JUnit 5? I guess that the corresponding mechanism of `GUITestRunner` would be a Jupiter extension?

Start by reading the existing GUITestRunner and AssertJSwingJUnitTestCase mechanisms mentioned in the issue, then compare their responsibilities with the requested JUnit 5 Jupiter extension. Define the supported JUnit 5 integration and its acceptance criteria before locating the relevant implementation and tests; done means equivalent support is covered by passing tests.

Vom Indexierungsmodell aus dem Issue-Text verfasst.