JavaScript callback that triggers when installation is complete

Let me start by saying this is an excellent and useful tool; however, I wish it could be more configurable. I do not see any documentation on how to add a JavaScript callback on the complete installation process. Our firmware operates as an Access Point and does not provide a terminal. The option to open the terminal causes confusion among the users installing the firmware. I would like to remove this option and instead have a JavaScript callback that triggers when installation is complete.