Include supporting events in the capture and bubble phases

I think it would be useful to test that libraries supporting custom elements include the ability to listen for events from either the capture or the bubble phase.

We recently ran into an issue where the [Angular Framework can only listen to bubble events](https://github.com/angular/angular/issues/11200) while [Angular Elements can only emit capture phase events](https://github.com/angular/angular/issues/39489). In this case the Angular Framework was not able to easily consume arbitrary custom elements (created by Angular Framework).