Split long line

Author: MariaSolOs

book/src/development/adding_lints.md

@@ -146,7 +146,8 @@ For cargo lints, the process of testing differs in that we are interested in the
 manifest.
 
 If our new lint is named e.g. `foo_categories`, after running `cargo dev
-new_lint --name=foo_categories --type=cargo --category=cargo` we will find by default two new crates, each with its manifest file:
+new_lint --name=foo_categories --type=cargo --category=cargo` we will find by
+default two new crates, each with its manifest file:
 
 * `tests/ui-cargo/foo_categories/fail/Cargo.toml`: this file should cause the
   new lint to raise an error.