Revise DeepSeek Sparse Attention content for improved clarity and engagement

- Updated the subtitle for better readability and accuracy.
- Enhanced the introduction with a clear prerequisite section for understanding attention mechanisms.
- Added new links to GitHub and a call to action for joining the open research efforts.
- Streamlined the explanation of the DeepSeek architecture, emphasizing its efficiency in reducing attention complexity.
- Included updated video resources and clarified the relationship between the new architecture and existing models.

Author: vukrosic