rust-learning-journey/ch4.md

• add text to a string
• try reassigning the value of a variable to another one, using different types, and see what the compiler says
• try passing a String instance and/or a Vector to a function which mutates it
• borrow a non-mutable reference and store it in a var, then print a value made from it (e.g. add one to it)
• use slicing to get the first word in a multi-word string and print it
• use assert_eq! to prove what slicing actually does;