Make Bluetooth dependencies optional

To install with Bluetooth dependencies, install nxt-python[bluetooth].
You can also install PyBluez yourself.

There is sadly still no release of PyBluez for recent Python versions,
drop it for now.

Author: schodet

setup.cfg

@@ -31,8 +31,12 @@ scripts =
 python_requires = >=3.8
 install_requires =
 	pyusb >= 1.2.1
+
+[options.extras_require]
+bluetooth =
 	pybluez >= 0.23; platform_system == 'Linux'
 	pybluez >= 0.23; platform_system == 'Windows'
+	pybluez >= 0.23; platform_system == 'Darwin'
 
 [flake8]
 max-line-length = 88