Support Thymeleaf

## Feature Request

### Description of Problem:
We have a lot of Thymeleaf assets, so we made a custom template engine using Thymeleaf .
But when the BDK is updated, these custom components also need to follow the details. (e.g. #686)
When Thymeleaf is supported natively by the BDK, we can safely update to the latest BDK, so we can concentrate on creating bots.