add property date_created for drive/file nodes

[bridystone]

Data is available in iCloud-Reponse, but not yet available via API interface

Proposed change

The property dateCreated is not yet avaialble via the API for file items

Type of change

• [ ] Dependency upgrade
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New service (thank you!)
• [X] New feature (which adds functionality to an existing service)
• [ ] Breaking change (fix/feature causing existing functionality to break)
• [ ] Code quality improvements to existing code or addition of tests
• [ ] Documentation or code sample

Example of code:

file_obj = icloud.drive[fileName]
print(file_obj.date_created)   # <-- this is new!
print(file_obj.date_modified)

Additional information

• This PR fixes or closes issue: fixes #361
• This PR is related to issue: #361

Checklist

• [X] The code change is tested and works locally.
• [x] Local tests pass. Your PR cannot be merged unless tests pass
• [x] There is no commented out code in this PR.
• [ ] Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• [ ] Documentation added/updated to README