Improve student project and contribution guidance

[sauravsingla]

What changed

• added a structured anomaly-detection project checklist for learners;
• linked the checklist from the main README;
• added a central documentation index;
• documented notebook quality and reproducibility standards;
• added focused issue templates for notebook problems and documentation suggestions;
• added a pull request checklist for educational and code contributions.

Why

The repository supports an established Udemy course, so the original notebook names and lecture flow remain intact. These additions improve the experience around the course without breaking existing student references.

Learner impact

Students now have clearer guidance for completing exercises, preparing portfolio projects, reporting notebook problems and understanding what makes an anomaly-detection analysis reproducible and responsible.

Validation

This change is documentation and repository-maintenance focused. Existing source code, notebooks, datasets and CI configuration are unchanged.