This pull request focuses on improving the documentation structure, readability, and accuracy for the E3SM-Unified project. Key updates include the addition of new sections, restructuring existing content, and refining package details for clarity.

Documentation Restructuring and Additions:

• Created new sections for "Release Workflow" (docs/releasing/index.md), "Creating Release Candidates" (docs/releasing/creating-rcs/index.md), and "Deployment and Testing" (docs/releasing/testing/index.md) to better organize the release process and testing documentation. [1] [2] [3]
• Moved and updated content from standalone markdown files (e.g., creating-rcs.md, testing/overview.md) into the newly created sections, improving navigation and clarity. [1] [2]

Refinement of Package Details:

• Updated the package catalog in docs/packages.md to split version constraints for Python versions into separate rows, enhancing readability. Additional explanatory text was added for better understanding of the table format. [1] [2] [3] [4]

Navigation and Linking Improvements:

• Fixed or updated internal links across multiple files to reflect the new structure, ensuring accurate navigation (e.g., linking to creating-rcs/overview.md instead of creating-rcs.md). [1] [2] [3] [4]

Build Process Enhancements:

• Enhanced the Sphinx build process in docs/Makefile by adding stricter error handling (-nW --keep-going) to ensure that warnings are treated as errors.

Minor Content Updates:

• Adjusted the table of contents depth in docs/index.md for better focus and removed outdated or redundant entries.
• Simplified the title in docs/packages.md for consistency.

These changes collectively improve the usability, maintainability, and accuracy of the documentation.