Provide promise-based methods instead of callback style

[jalcine]

A lot of the current examples lean on callback-style approaches which is (more or less) not a needed design pattern for the project. More recent version of Node and browsers support promises.

• CanIUse: https://caniuse.com/mdn-javascript_builtins_promise_any
• https://developer.mozilla.org/en-us/docs/Web/JavaScript/Reference/Global_Objects/Promise