Add types to promisify-port.js

[marc136]

This PR is a step towards #125, and adds types to lib/promisify-port.js.

I was not sure about the descriptive comments, feel free to change them however you see fit.

I never wrote jsdoc comments to such an extent before, adding a .d.ts file would have been easier for me.
Thank you for the challenge 😆

[marc136]

I realized later, that adding .d.ts definition files is also possible. So I extracted the hardly readable JSDoc types to types/promisify-port.d.ts.

[jfmengels]

Hey @marc136! Thanks for looking at this!
This all looks good to me 😊
(And yes, the .d.ts. files are nicer 😁 )