Code examples is blank

[scarrazza]

I thiknk something is not working well for the notebook example, see https://qibo.science/qibotn/latest/code-examples/index.html.

[scarrazza]

In fact, the notebook is missing and the deps for docs are not including matcha and qiskit. @MatteoRobbiati please have look. If depencies are a bit issue, please revert your PR with the example folder.