README: document how to build the ISO

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@2950 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9
Add VLC as it has Wayland capabilities

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@2951 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9