Normalize structure: Add Introduction and Testing sections (#227)

[anikchand461]

Changes

This PR addresses #227 by normalizing the structure of the "Reproducible ML with Cloud Pods" tutorial:

• Added ## Introduction heading around the existing overview paragraphs (no content changes).
• Inserted ## Testing the Application section after "Deploying the Lambda functions" (before "Creating a Cloud Pod"), including:
  • Reproducible invocation commands.
  • Expected outputs/logs for training/inference (e.g., sample predictions, ~96.9% accuracy on digits dataset).
  • Validation steps for Pod restore to confirm reproducibility.

No other content was modified—preserved all original code, diagrams, and notes.

Testing

• Verified locally with npm run dev (renders cleanly at /docs/aws/tutorials/reproducible-machine-learning-cloud-pods/).
• Built with npm run build—no errors.

Hacktoberfest contribution! Excited to help improve the docs.

Closes #227.