Promise should be optional.

[TimUnderhay]

Apologies if I've misinterpreted the documentation, but in V3 it seems that debounce now always returns a promise, no matter what. This breaks debounce in contexts where a Promise-wrapped result isn't expected, such as option parameters in 3rd-party libraries which expect a callback function. There should ideally be both a callback-based and a promise-based version of the function. I hope you don't mind the suggestion. Thanks!

[chodorowicz]

No need for apologies! Thanks for the feedback! 🙂 I'm open to this change and have two version of the debounce function.
Could you provide a specific example where it fails when promise is returned? You could use https://codesandbox.io/ or https://stackblitz.com/ to create an example? It would be useful to recreate the issue and I would be able to verify that a fix really fixes the issue.
Thanks!