Adding DEVICE_TYPE_ACCESSORY to enum

+ Adding Accessory icons for light and dark theme
+ Adding entry into OpenRGBDialog2 to display icon
+ Creating `Accessory` category in "Supported Devices"

RGBController/RGBController.h

@@ -178,6 +178,7 @@ enum
     DEVICE_TYPE_STORAGE,
     DEVICE_TYPE_CASE,
     DEVICE_TYPE_MICROPHONE,
+    DEVICE_TYPE_ACCESSORY,
     DEVICE_TYPE_UNKNOWN,
 };