Explict callback types in option

[offich]

fix: #398

Description

Improving callback types in option:

interface Options {
...
  beforeString?: (string: String, instance: TypeIt) => void | ((string: String, instance: TypeIt) => Promise<void>);
  afterString?: (string: String, instance: TypeIt) => void | ((string: String, instance: TypeIt) => Promise<void>);
  beforeStep?: (instance: TypeIt) => void | ((instance: TypeIt) => Promise<void>);
  afterStep?: (instance: TypeIt) => void | ((instance: TypeIt) => Promise<void>);
  afterComplete?: (instance: TypeIt) => void | ((instance: TypeIt) => Promise<void>);
...
}

Type of Change

• It's a bug fix.
• It's a new feature (without breaking changes).
• It's a breaking change.

Checklist

• Provided detailed description of the issue above.
• Updated tests where appropriate.

License Agreement

[] By submitting this code, I'm aware that, if merged, it will be used as part of a commercial project. By submitting this pull request, I am aware that I'm giving my consent for my code to become a part of TypeIt or any of its related packages, and for it to be used and sold commercially.