The function kendo.chat.registerTemplate as mentioned here: https://docs.telerik.com/kendo-ui/controls/conversational-ui/chat/chat-items#custom-templates is missing in API Reference and the Typescript Definitions.
It would also be nice to have it documented in functions that are using the templates, for example the "message.type" parameter in https://docs.telerik.com/kendo-ui/api/javascript/ui/chat/methods/rendermessage