Rustlings 6.5.0

Added

• Check that Clippy is installed before initialization

Changed

• Upgrade to Rust edition 2024
• Raise the minimum supported Rust version to 1.88
• Don't follow symlinks in the file watcher
• dev new: Don't add .rustlings-state.txt to .gitignore

Fixed

• Fix file links in VS Code
• Fix error printing when the progress bar is shown
• dev check: Don't check formatting if there are no solution files