Develop docstrings for rockmag.py functions that currently lack them

[Swanson-Hysell]

Issue:

Several functions in rockmag.py currently lack docstrings. To improve code readability and maintainability, we should add docstrings to all functions.

Docstring Format

Use Google-style docstrings, with the following conventions:

• Use Parameters instead of Args
• Include Returns with types and descriptions
• Line length should conform to Black formatting (~88 characters)

Examples of undocumented functions

• interactive_verwey_estimate
• interactive_goethite_removal