fix: prevent identifier extraction as event names, support custom Event classes

[binlabs]

Fixes #149

1. The analyzer incorrectly extracted identifiers as event names when dispatching custom event classes (e.g., extracting "someArg" from new MyEvent(someArg)).
2. Now parses custom Event class constructors to extract the actual event name from the super() call.

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[binlabs]

I just realized that naming these fixtures "custom-event" may have been confusing, because they are really subclasses of either Event or CustomEvent.

So I just renamed the fixtures and amended the commit, just FYI.

[web-padawan]

We have also noticed this issue with the incorrect eventName extraction as event name in the following code:

  __dispatchCustomEvent(eventName, item, value) {
    if (!item) {
      return;
    }
    this.dispatchEvent(
      new CustomEvent(eventName, {
        detail: {
          item,
          value,
        },
      }),
    );
  }

IMO it would be good to get this fix merged, maybe it would help to split into 2 PRs. @thepassle WDYT?