Add shebang for updatePlugin

bin/updatePlugin

@@ -1,3 +1,4 @@
+#!/usr/bin/sh
 plugin=$(wp plugin list 2> /dev/null | grep available | head -n 1 | awk '{print $1}')
 echo "$plugin"
 versions=$(wp plugin update $plugin 2> /dev/null | tail -n 2 | head -n 1 | awk '{print $2 "->" $3}')