I copied the lines you used as an example and put the rpy file in the game folder and made a new game because I was having issues with the code being registered. But it still can't be registered, renpy sees it as an unknown tag. I've used other text tags so I'm thinking there's an issue within the file? Not sure if I'm wrong but I just wanted to let you know ^^
2 days ago (+1)
It’s all about the init python priority here, since
I personally keep the file in the libs folder for preloading.
Other than that, it’s a basic way to use text shaders
through a single text tag ^^