Features

• Hint comments in exercises now also include a reference to the hint watch mode subcommand.
• intro1: Added more hints to point the user to the source file.
• variables: Switched variables3 and variables4.
• Moved vec and primitive_types exercises before move_semantics.
• Renamed vec to vecs to be more in line with the naming in general.
• Split up the collections exercises in their own folders.
• vec2: Added a second part of the function that provides an alternative, immutable way of modifying vec values.
• enums3: Added a hint.
• Moved strings before modules.
• Added a strings3 exercise to teach modifying strings.
• Added a hashmaps3 exercise for some advanced usage of hashmaps.
• Moved the original quiz2 to be strings4, since it only tested strings anyways.
• Reworked quiz2 into a new exercise that tests more chapters.
• Renamed option to options.
• options1: Rewrote parts of the exercise to remove the weird array iteration stuff.
• Moved generics3 to be quiz3.
• Moved box/arc exercises behind iterators.
• iterators4: Added a test for factorials of zero.
• Split threads1 between two exercises, the first one focusing more on JoinHandles.
• Added a threads3 exercises that uses std::sync::mpsc.
• Added a clippy3 exercises with some more interesting checks.
• as_ref_mut: Added a section that actually tests AsMut.
• Added 3 new lifetimes exercises.
• Added 3 new traits exercises.

Bug Fixes

• variables2: Made output messages more verbose.
• variables5: Added a nudging hint about shadowing.
• variables6: Fixed link to book.
• functions: Clarified the README wording. Generally cleaned up some hints and added some extra comments.
• if2: Renamed function name to foo_if_fizz.
• move_semantics: Clarified some hints.
• quiz1: Renamed the function name to be more verbose.
• structs1: Use an integer type instead of strings. Renamed "unit structs" to "unit-like structs", as is used in the book.
• structs3: Added the panic! statement in from the beginning.
• errors1: Use is_empty() instead of len() > 0
• errors3: Improved the hint.
• errors5: Improved exercise instructions and the hint.
• errors6: Provided the skeleton of one of the functions that's supposed to be implemented.
• iterators3: Inserted todo! into divide() to keep a compiler error from happening.
• from_str: Added a hint comment about string error message conversion with Box<dyn Error>.
• try_from_into: Fixed the function name in comment.

Removed

• Removed the legacy LSP feature that was using mod.rs files.
• Removed quiz4.
• Removed advanced_errs. These were the last exercises in the recommended order, and I've always felt like they didn't quite fit in with the mostly simple, book-following style we've had in Rustlings.

Housekeeping

• Added missing exercises to the book index.
• Updated spacing in Cargo.toml.
• Added a GitHub actions config so that tests run on every PR/commit.