Report: add CreateBuffer method that returns an initialized report buffer

Signed-off-by: Benedek Kupper <kupper.benedek@gmail.com>

Author: benedekkupper

HidSharp/Reports/Report.cs

@@ -127,6 +127,13 @@ void ComputeLength()
             _computed = true;
         }
 
+        public byte[] CreateBuffer()
+        {
+            byte[] buffer = new byte[Length];
+            buffer[0] = ReportID;
+            return buffer;
+        }
+
         public DeviceItem DeviceItem
         {
             get;