Fix rendering with sort

[LuizMacedo]

This pull request refactors the logic for grouping and displaying exercises by topic in the index.md file. The changes improve clarity and maintainability by introducing a new sorted_groups variable to handle the ordering of grouped exercises.

Refactoring of exercise grouping logic:

• Updated the topic_order variable to use capitalized topic names ("Basic,Intermediate,Advanced,Expert") for consistency.
• Introduced a sorted_groups variable to store pre-sorted groups, replacing the inline filtering and sorting logic in multiple loops. This simplifies the code and avoids redundant operations.
• Adjusted the loops to iterate over sorted_groups instead of dynamically filtering grouped_exercises during each iteration.
• Removed unused or redundant conditional checks and lines for improved readability.

[Copilot]

Pull Request Overview

This pull request refactors the exercise grouping and sorting logic in index.md to improve code clarity and maintainability. The changes eliminate redundant filtering operations and introduce a more structured approach to handling sorted exercise groups.

• Standardized topic naming by capitalizing topic names in topic_order
• Introduced sorted_groups variable to pre-sort groups once instead of filtering repeatedly
• Simplified loop logic by removing redundant conditional checks and inline filtering