Mention pytest-custom_exit_code in the docs
Mention pytest-custom_exit_code in the docs

Related to #5689

nicoddemus/pytest,nicoddemus/pytest,The-Compiler/pytest,RonnyPfannschmidt/pytest,tomviner/pytest,pytest-dev/pytest,tomviner/pytest,Akasurde/pytest,alfredodeza/pytest,The-Compiler/pytest,markshao/pytest