Add -p|--progress option to show progress and ETA

Change-Id: I14d9225bae6ca3af2ccc129399f51f6440947f49
diff --git a/Readme.pod b/Readme.pod
index c097fd2..8341149 100644
--- a/Readme.pod
+++ b/Readme.pod
@@ -99,6 +99,11 @@
 
   tei2korapxml -tk corpus1.i5.xml corpus2.i5.xml
 
+=item B<--progress|-p>
+
+Show a progress bar (including ETA).
+This option is ignored if valid input is not read from a file.
+
 =item B<--output|-o>
 
 The output zip file to be created. If no specific output is defined,