Add ABIDE tutorial

[zaRizk7]

Adds a tutorial for neuroimaging using PyKale and Nilearn to reduce phenotypic dependencies of functional connectivity features.

• Notebook structure consisting of:
  1. Introduction and Objective
  2. Setup (Warning Supression, Required Packages, and Helper Functions)
  3. Pipeline
     1. Data Loading and Preprocessing
     2. Feature Extraction
     3. Model Definition
  4. Training and Validation
  5. Evaluation
  6. Interpretation
• Adds descriptions for each sections.
• Includes biomarker visualization and model comparison.

[shuo-zhou]

The PR is approved for merging to continue development. Overall, it looks like a scikit-learn tutorial rather than a PyKale-specific one. We should consider moving some functions into PyKale itself. Please refer to the current heart or brain examples in PyKale.