Heya 
Welcome!
It’s likely that the module is fully initialized after the ready hook has already been called.
You are doing it right, I believe 
Check this screenshot for another example.
You can use a different hook, like sightRefresh to test.
Alternative to world scripter
As an edit to this post, another way to add world scripts (if you need them to run very early on in Foundry’s startup) is to export the world (How to Export Worlds and Compendium Modules from The Forge), edit its world.json file and add your world scripts locally, and then re-import the world with the Import Wizard.