Kloppy

Pull requests merged:
- Add related events and next/prev with more easy filtering ([129](https://github.com/PySport/kloppy/pull/129))

- Improve contribution guide ([123](https://github.com/PySport/kloppy/pull/123))
- Fix extraction of foul committed events ([126](https://github.com/PySport/kloppy/pull/126))
- Add formation statebuilder + read opta/statsbomb formation events ([125](https://github.com/PySport/kloppy/pull/125))

- Implement simpler api ([118](https://github.com/PySport/kloppy/pull/118))

- Opta serializer improvements ([119](https://github.com/PySport/kloppy/pull/119))

- Don't break when wyscout doesn't include end position of shot/pass

Fix import for second spectrum