Add a Comprehensive Roadmap for Data Structures and Algorithms (DSA)

[Code-ashiq]

Hello,

I’d like to propose adding a structured DSA (Data Structures and Algorithms) roadmap to this repository. The goal is to provide learners with a clear and progressive path to mastering core DSA topics, which aligns with the repository’s mission to make computer science education accessible and organized.

The roadmap would be added as a dsa_roadmap.md file or placed in a new roadmaps/ directory for better organization and future expansions.

Please let me know your thoughts or if you have preferences regarding structure or format before I proceed with a pull request.

Thanks!