Some small features implemented

Feature list:

• Level Progress Saving: Your progress is now saved — you no longer have to restart levels when revisiting.
• Resizable Sub-windows: Adjust the size of each section (Code, Output, Goal, Input) to your preference.
• Clearer Code Block Separators: Improved visibility of code block dividers and clearer movement restrictions.
• Reset Progress Option: Start fresh anytime by deleting all your progress.