Add problem statement and ecosystem sections to docs

[walkerbdev]

• Add problem statement before Key Features explaining challenges of tracking experiments with changing parameters, code, dependencies, and environment
• Add ecosystem/alternatives section with links to MLflow, Weights & Biases, Neptune.ai, Comet ML
• Updated both README.md and docs/user-guide.rst for consistency

Description

Please include a summary of the changes and the related issue.

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ x] Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.
N/A

• Test A
• Test B

Checklist

• [x ] My code follows the style guidelines of this project
• [x ] I have performed a self-review of my own code
• [x ] I have commented my code, particularly in hard-to-understand areas
• [ x] I have made corresponding changes to the documentation
• [ x] My changes generate no new warnings
• [ x] I have added tests that prove my fix is effective or that my feature works
• [ x] New and existing unit tests pass locally with my changes
• [ x] I have run pre-commit run --all-files and it passes