Docs update with DocStringExtensions

[jb-mackay]

Purpose and Content

Adds DocStringExtensions.jl to the src directory. Primarily uses DocStringExtensions.@template to create uniform docstrings. Also updates the API docs.

Benefits and Risks

DocStringExtensions will make our docs more robust to code changes (signature updates, field updates, etc). Using @template also ensures that the same information is included in docstrings for the same types of info (methods, types, etc) and streamlines what we need to write.

Linked Issues

Closes #64
Part of #84

PR Checklist

• This PR has a corresponding issue OR is linked to an SDI.
• I have followed CliMA's codebase contribution and style guidelines OR N/A.
• I have followed CliMA's documentation policy.
• I have checked all issues and PRs and I certify that this PR does not duplicate an open PR.
• I linted my code on my local machine prior to submission OR N/A.
• Unit tests are included OR N/A.
• Code used in an integration test OR N/A.
• All tests ran successfully on my local machine OR N/A.
• All classes, modules, and function contain docstrings OR N/A.
• Documentation has been added/updated OR N/A.