added readme.txt file

git-svn-id: https://plugins.svn.wordpress.org/convert-to-bangla-date/trunk@806063 b8457f37-d9ea-0310-8a92-e5e31aec5664
added convert-to-bangla-date.php file

git-svn-id: https://plugins.svn.wordpress.org/convert-to-bangla-date/trunk@806064 b8457f37-d9ea-0310-8a92-e5e31aec5664