I am afraid currently Kendo UI Chart does not support baselines. Actually there is a similar idea shared at our UserVoice page - if you wish you may cast a vote, leave a comment or monitor the community's interest in it here. The more votes the suggestion collects, the higher priority will have.
Meanwhile as a possible workaround I can suggest you adding two additional line series in order to achieve the desired outcome.
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI