Adding pytest-cov for use

{{cookiecutter.package_name}}/pyproject.toml

@@ -16,6 +16,7 @@ black = "==22.6"
 flake8 = "==3.8.4"
 pre-commit = "*"
 pytest = "*"
+pytest-cov = "*"
 pytest-sugar = "*"
 sphinx = "*"
 sphinx-autobuild = "*"