Adds comma

Co-authored-by: Mark "Murch" Erhardt <[email protected]>

Author: EthanHeilman

bip-0347.mediawiki

@@ -20,7 +20,7 @@ This document is licensed under the 3-clause BSD license.
 
 ==Specification==
 
-When evaluated the OP_CAT instruction:
+When evaluated, the OP_CAT instruction:
 # Pops the top two values off the stack,
 # concatenates the popped values together in stack order,
 # and then pushes the concatenated value on the top of the stack.