Usual concerns about new methods

Author: Philippe-Cholet

CONTRIBUTING.md

@@ -5,6 +5,7 @@ Please check the minimum version of Rust we use in `Cargo.toml`.
 
 _If you are proposing a major change to CI or a new iterator adaptor for this crate,
 then **please first file an issue** describing your proposal._
+[Usual concerns about new methods](https://github.com/rust-itertools/itertools/issues/413#issuecomment-657670781).
 
 To pass CI tests, your code should be free of "compiler warnings" and "rustfmt" formatted.
 And it might become mandatory that your code changes are free of "clippy warnings"