Support OR combinator

[XVincentX]

It would be very helpful if Spectral could support some sort of OR combinator where I can define multiple functions to apply. If one of them passes, the validation is marked as ✅

  given: >-
      $...parameters[*].name
  then:
    or:
    - function: casing
      functionOptions:
        type: snake
    - function: casing
      functionOptions:
        type: camel

[ioggstream]

Probably a general thought on other logic functions could be useful (eg. negating function, negating then). Such a mechanism allows to implement or like that:

then_not:
- function: casing
  expect: false
  functionOptions: {type: snake}
- ...

via De Morgan.

[philsturgeon]

We talked about having a "not" today, which is probably related to this.