Standardize README formatting and update resource links

[fs0ci5ty]

This PR improves the overall readability and maintenance of the README.md file by:

1. Standardizing Link Formatting: All resource entries have been converted from plain text or hybrid formats to the standard Markdown list link format: - [Resource Name](URL).
2. Updating Headings: Ensured consistent heading levels across the document, with main categories using ### and subcategories using ####.
3. Fixing Broken/Redirected Links: Audited key links (especially from major providers like EdX, Microsoft, and Google AI) and updated them to their current, functional URLs.
4. Content Refinement: Replaced identified dead links (like the Microsoft Principles of ML course) with relevant, high-quality alternatives from the same platform.
5. Consistency: Standardized the naming and structure of links for Udacity and Kaggle courses.

---

PR created automatically by Jules for task 599802174919615997 started by @fs0ci5ty

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.