Added credits for Peter Kacherginsky

doc/scapy/backmatter.rst

@@ -6,6 +6,7 @@ Credits
 - Philippe Biondi is Scapy's author. He has also written most of the documentation.
 - Fred Raynal wrote the chapter on building and dissecting packets.
 - Sebastien Martini added some details in "Handling default values: automatic computation".
+- Peter Kacherginsky contributed several tutorial sections, one-liners and recipes.
 - Dirk Loss integrated and restructured the existing docs to make this book. 
   He has also written the installation instructions for Windows.