Restore optional NumPy dependency (#162)

Author: adamtheturtle

pyproject.toml

@@ -19,6 +19,9 @@ classifiers = [
 requires-python = ">=3.7"
 dependencies = ["cffi"]
 
+[project.optional-dependencies]
+NumPy = ["numpy"]
+
 [project.urls]
 Documentation = "http://jackclient-python.readthedocs.io/"
 Repository = "https://github.com/spatialaudio/jackclient-python/"