能否出一个自定义模板的demo或者教程？

希望出一个定义模板的demo和教程，现阶段官网的示例和文档有点少，自定义模板不知如何下手，希望出一个demo，叫写一个简单的MyCard模板，然后加上如何打包成JS的demo。

Start by reviewing the existing examples and documentation on the ChatUI website, then locate the custom-template entry points in the repository. Create a simple MyCard template demonstration and document how to package it as JavaScript; done means the example and tutorial are available and understandable to users starting from the current sparse guidance.

Written by the indexing model from the issue text.