add numpydoc to test environment

Author: murrayrm

.github/conda-env/test-env.yml

@@ -9,3 +9,4 @@ dependencies:
   - numpy
   - matplotlib
   - scipy
+  - numpydoc

pyproject.toml

@@ -40,7 +40,7 @@ dynamic = ["version"]
 packages = ["control"]
 
 [project.optional-dependencies]
-test = ["pytest", "pytest-timeout", "ruff"]
+test = ["pytest", "pytest-timeout", "ruff", "numpydoc"]
 slycot = [ "slycot>=0.4.0" ]
 cvxopt = [ "cvxopt>=1.2.0" ]