Ensure CMEW can be run at other sites

[Theo Geddes (mo-tgeddes)]

Closes #55.

PR creation checklist

• Does the feature branch name follow the format <issue_number>_<short_description_of_feature>?
• Does the PR title exactly match with the issue title?
• Have appropriate reviewers been added to the PR?
• Has the PR been assigned to the developer?
• Has the Climate Model Evaluation Workflow (CMEW) project been added to the PR?
• Has the appropriate milestone been added to the PR?

Review checklist

• Do the changes in this PR address the above issue / have all acceptance criteria been met?
• Do the changes follow the recommendations in the wiki: Developer Guide?
• Do all the tests pass? (the tests are not run by the GitHub workflow)
• Has the documentation been updated appropriately?
• Do the HTML pages render correctly?
• Do the steps in the "Quick Start" section work?