Updated Recursiveness (markdown)

Recursiveness.md

@@ -16,6 +16,9 @@ To check files with one of multiple extensions:
 
 ```
 # Bash 4+
+# globstar makes ** recursive.
+# nullglob will prevent one of the extension pattens from appearing in the arg list
+# if they don't match.
 shopt -s globstar nullglob
 shellcheck /path/to/scripts/**/*.{sh,bash,ksh}