Add Hello Algo book to Data Structures section

[yokodrea]

This PR adds the open-source book "Hello Algo" to the Data Structures section.

link: https://www.hello-algo.com/en/chapter_preface/about_the_book/

Reasoning (aligned with repo values):

• Personally tested and currently using it for learning DSA concepts.
• Beginner-friendly and simple, matches "less is more" and "simplicity" values.
• Free and open-source, accessible to everyone.
• Offers unique value compared to existing resources: animated illustrations + interactive runnable code.
• Helps improve both understanding and practical coding skills.