Changed

• vecs: Added links to iter_mut and map to README.md
• cow1: Changed main to tests
• iterators1: Formatted according to rustfmt

Fixed

• errors5: Unified undisclosed type notation
• arc1: Improved readability by avoiding implicit dereference
• macros4: Prevented auto-fix by adding #[rustfmt::skip]
• cli: Actually show correct progress percentages