Release Euclid clusters notebook

[troyraen]

• Copy https://github.com/IPAC-SW/ipac-sp-notebooks/blob/main/euclid-clusters/euclid_clusters_tutorial.md into this repo.
• Merge https://github.com/IPAC-SW/ipac-sp-notebooks/blob/main/euclid-clusters/.gitignore with the .gitignore in this repo.
• Delete the ipac-sp-notebooks directory https://github.com/IPAC-SW/ipac-sp-notebooks/tree/main/euclid-clusters.
• Add an entry to deploy_to_fornax_manifest.in to release this notebook.

#283 should go at the same time, so please coordinate.