docs: explicitely refer to charmcraft dependency

[deusebio]

fixes #156

[motjuste]

Thank you for the explanation. It will also be helpful to have a clear list like:

The following will be required to execute the UATs:

- Python 3.10+
- Tox [preferably with specific version or range] (to drive the tests; it will install and use Poetry to install the required Python packages)
- Juju [preferably with specific version or range] (assumed to have been used for deploying Charmed Kubeflow)
- charmcraft [preferably with specific version or range] (for validating the deployment at a high level).

I also notice that further down the README, the instructions still state to install and use Python 3.8. Maybe that's a hold-over from testing 1.7 or 1.8? That should also be updated sometime soon.