update readme.txt FAQ

git-svn-id: https://plugins.svn.wordpress.org/jm-dashicons-shortcode/trunk@856517 b8457f37-d9ea-0310-8a92-e5e31aec5664
add short footage + fix some bugs and delete useless quicktags

git-svn-id: https://plugins.svn.wordpress.org/jm-dashicons-shortcode/trunk@856582 b8457f37-d9ea-0310-8a92-e5e31aec5664