Support for case-sensitivity

[dvh]

AFAIK rules currently don't have a way to match on case-sensitivity. For example, we now have to use this workaround to check if there is an api-version header:

nlgov:missing-version-header:
  severity: error
  given: $..[responses][?(@property && @property.match(/(2|3)\d\d/))][headers]
  then:
    function: or
    functionOptions:
      properties:
        - API-Version
        - Api-Version
        - Api-version
        - api-version
        - API-version
  message: "Return the full version number in a response header."

I would like to think about a way to deal with this, so we don't need this workaround anymore.