Render notebooks for the documentation

To have some visual help, we should enable the notebook rendering when building the documentation. This can be achieved by setting the [nb-config](https://myst-nb.readthedocs.io/en/latest/computation/execute.html#notebook-execution-modes) key found in [conf.py](https://github.com/aiidalab/aiidalab-widgets-base/blob/eeb00a352ed77beadcc38fed66ddfaa5e6d24131/docs/source/conf.py#L30) to `force`.

The issue here is that AiiDA will have to be installed on the documentation server, as some notebooks require access to the AiiDA objects.