contrib/simtrace.lua: Add header with author/description/usage

Change-Id: I56574741cd77436f9f452420677c00d8049a50cc
diff --git a/contrib/simtrace.lua b/contrib/simtrace.lua
index 09ee9e6..d05ff0a 100644
--- a/contrib/simtrace.lua
+++ b/contrib/simtrace.lua
@@ -1,3 +1,9 @@
+-- wireshark LUA dissector for the SIMtrace USB protocol
+-- (C) 2021 by sysmocom - s.f.m.c. GmbH, Author: Eric Wild
+-- SPDX-License-Identifier: GPL-2.0+
+--
+-- Usage: Put this into your ~/.wireshark/init.lua [or include it from there]
+
 usb_simtrace_protocol = Proto("USB_simtrace",  "USB simtrace protocol")