split off dependencies for optional installation (#546)

* add inheritance diagrams to all printers and exceptions
* split off printer implementations into separate files
* add wrapper that thros RuntimeError if not importable
* add dependency check for lp
* add dependency check for pyserial
* added check for usability
* import Win32Raw
* include WIn32Raw in documentation
* enable all extras on tox
* update github workflow

setup.cfg

@@ -35,10 +35,8 @@ python_requires = >=3.8
 zip_safe = false
 include_package_data = true
 install_requires =
-    pyusb>=1.0.0
     Pillow>=2.0
     qrcode>=4.0
-    pyserial
     python-barcode>=0.9.1,<1
     setuptools
     six
@@ -60,6 +58,21 @@ tests_require =
     flake8
     sphinxcontrib-spelling>=7.2.0
 
+[options.extras_require]
+usb =
+    pyusb>=1.0.0
+serial =
+    pyserial
+cups =
+    pycups
+win32 =
+    pywin32; platform_system=='Windows'
+all =
+    pyusb>=1.0.0
+    pyserial
+    pycups
+    pywin32; platform_system=='Windows'
+
 [flake8]
 exclude = .git,.tox,.github,.eggs,__pycache__,doc/conf.py,build,dist,capabilities-data,test,src/escpos/constants.py
 max-line-length = 120