move screenshot 1 to assets

git-svn-id: https://plugins.svn.wordpress.org/ragic-shortcode/trunk@888634 b8457f37-d9ea-0310-8a92-e5e31aec5664
more screenshot 2 to assets

git-svn-id: https://plugins.svn.wordpress.org/ragic-shortcode/trunk@888637 b8457f37-d9ea-0310-8a92-e5e31aec5664