gh-142: caching of comet files

[AndreaPezzotta]

🚀 Pull Request Checklist

✅ Summary

Modified ci.yml to make C.I. workflow to load cached COMET files

🏗 Related Issues

• Resolves Caching of COMET files #142

✅ PR Checklist for Developers

• I have titled this PR before merging as "gh-#:", where "#" represents the task it closes
• I have run locally pre-commit using pre-commit run --all-files
• I have tested my changes locally
• No new warnings or errors introduced
• I have updated documentation (if applicable)
• My changes do not introduce breaking changes
• I have added tests (if applicable)
• I have consistently updated the GitHub information for the project, including milestones, task types, and other relevant details.

✅ PR Checklist for Reviewers

• The next PR targets the correct branch
• CI tests have run and passed for the latest commit on the source branch
• Check that the code can still be installed if new packages are imported
• If necessary, the notebooks in the playground will be updated in a corresponding follow-up PR
• Coverage percentage is retained or increased
• Quality of new/changed code is acceptable
• Quality of new/changed unit tests is acceptable
• No data files have been included in the commits
• Implementation follows the agreed task description point by point
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• Check that any added folder/file has been added to the README.md file
• Check that the documentation has been updated accordantly
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[chiaramoretti]

seems to be working well 🥳 ! merging