moving screenshot 1 to assets


git-svn-id: https://plugins.svn.wordpress.org/embed-chessboard/trunk@972695 b8457f37-d9ea-0310-8a92-e5e31aec5664
moving screenshot 2 to assets


git-svn-id: https://plugins.svn.wordpress.org/embed-chessboard/trunk@972696 b8457f37-d9ea-0310-8a92-e5e31aec5664