Perfect! The Streamlabs .com website claims that their credits will automatically start upon opening up the page. Not true. I found it not working AT ALL actually. This script submitted by my friend Etrain, actually does exactly what you want it to do.

Provided you've set up your end credits to actually work, which you can test using the Test Roll credits to appear on your page without being online; once you get this extension set up and a hotkey on your keyboard or one of the streamdeck buttons to change your scene and open up the website using the link ending with "/credits?activate=true" it should work perfectly!