Module plugin template is misleading

[MCKRUZ]

Expected behavior:
I followed the template exactly and it can't do what it's claiming you can do. I would expect from the template that I could extend an existing module with a new function.
https://www.typescriptlang.org/docs/handbook/declaration-files/templates/module-plugin-d-ts.html

Actual behavior:
I am unable to extend the existing module with a new function.

https://github.com/MCKRUZ/TS-Plugin-HW