feat: arrayish given

[P0lip]

Checklist

• Tests added / updated
• Docs added / updated

Does this PR introduce a breaking change?

• Yes
• No

Currently we only allow a single JSON path expression to be provided at a time for each rule.
That limitation may lead to a situation where a complex json path expression needs to be provided in order to match all intended properties. In most cases, those expressions could be split into 2-3 that would be much simpler.

[jerzyn]

would this mean given could be a single value or an array? Or how do you envision that?
i.e. in JSON-Schema terms:

given:
  oneOf:
    - type: string
    - type: array
      items:
        type: string

[P0lip]

@jerzyn
That's right. I even used exactly the same schema in ruleset JSON schema 😅
https://github.com/stoplightio/spectral/pull/799/files#diff-1eb67ba0248f0910e2cd0525f69731dcR69-R79

[jerzyn]

i should do these examples professionally ;)

[nulltoken]

@P0lip Nit: From a reader's perspective, it's not very clear if, for the rule to pass, all the expressions have to satisfy the expectation or at least one of them.