Move descriptor_type argument to avoid API breakage

usb_protocol/emitters/descriptors/hid.py

@@ -106,4 +106,4 @@ class HIDDescriptor(ComplexDescriptorEmitter):
         report_descriptor = b"".join(report_descriptor)
         descriptor_len = len(report_descriptor)
         self.wDescriptorLength = descriptor_len
-        self._parent_descriptor.add_descriptor(report_descriptor, 0x22)
+        self._parent_descriptor.add_descriptor(report_descriptor, descriptor_type=0x22)

usb_protocol/emitters/descriptors/standard.py

@@ -177,14 +177,14 @@ class DeviceDescriptorCollection:
         return index
 
 
-    def add_descriptor(self, descriptor, descriptor_type=None, index=0):
+    def add_descriptor(self, descriptor, index=0, descriptor_type=None):
         """ Adds a descriptor to our collection.
 
         Parameters:
             descriptor      -- The descriptor to be added.
+            index           -- The index of the relevant descriptor. Defaults to 0.
             descriptor_type -- The type of the descriptor to be added. If `None`,
                                this is automatically derived from the descriptor contents.
-            index           -- The index of the relevant descriptor. Defaults to 0.
         """
 
         # If this is an emitter rather than a descriptor itself, convert it.