Add sound and license files

Add sound and license files

Grand_Central_Soundboard/Sound-licenses.txt

@@ -0,0 +1,13 @@
+The wav files for this guide listed below were obtained from http://soundbible.com/tags-train.html
+
+The files have the following attributions Creative Commons 3 license unless marked Public Domain:
+
+Steam Train Whistle by Daniel Simion
+Steam Train Sound by Daniel Simion 
+Railroad Crossing Bell by Brylon Terry 
+Cargo Train by Stephan Schutze
+Train Sound Indian Railways Public Domain by Satish Madiwale
+Train Honk Horn 2x Sound by Mike Koenig 
+Toy Train Whistle Sound Public Domain by KP 
+
+You can view the terms of the Creative Commons 3.0 license at https://creativecommons.org/licenses/by/3.0/us/