v0.2.0

This is a major step forward for this library.
Now, expression language is supported. Also, an experimental visualization is possible.
hat said, still not recommended to use in production.
But any feedback or contributions are very welcome :)

For details, have a look at https://github.com/nitram509/lib-bpmn-engine/issues?q=is%3Aissue+milestone%3Av0.2.0+is%3Aclosed