Update readme.txt and add for screenshot

git-svn-id: https://plugins.svn.wordpress.org/arabic-font/trunk@1008849 b8457f37-d9ea-0310-8a92-e5e31aec5664
change readme.txt for displaying code

git-svn-id: https://plugins.svn.wordpress.org/arabic-font/trunk@1008852 b8457f37-d9ea-0310-8a92-e5e31aec5664