add e2e tests

[mathe42]

In the example folder we have a vite project with multiple worker calls etc.

We should:

1. extend this to more examples also some with shared Workers.
2. create e2e tests with cypress to check if all examples work properly.
3. integrate that tests into github actions

You want to contribute to vite-plugin-comlink this issue is a good start (even if you didn't used e2e tests before).