Unsafe typing of PrintdCallbackArgs.launchPrint

[jraoult]

Using Function to type a function is not ideal in typescript and is now considered unsafe by typescript-eslint (see the rationale here: typescript-eslint/typescript-eslint#9108) so that calling launchPrint() now fails in my lint stage.

I checked the source code, and it turns out it should be pretty easy to fix by declaring launchPrint: () => void since it is not supposed to return anything.

I am happy to create a PR if you need me to.

[joseluisq]

Sure, feel free to contribute.