Note that this line (from the Yesod Book) will only include .lucius, .cassius, .hamlet, and .julius files.
$(widgetFile "resource/index")
So you need to implement a custom function using the Text.TypeScript stuff linked above.
Alternatively (I would never copy & paste), you can write a Makefile that generates the .julius files from .ts files using tsc. And then just call make before you recompile your Yesod app.