Add support uppercase wildcard character X in response code

[supertong]

https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#responsesObject

To define a range of response codes, this field MAY contain the uppercase wildcard character X. For example, 2XX represents all response codes between [200-299]. Only the following range definitions are allowed: 1XX, 2XX, 3XX, 4XX, and 5XX. If a response is defined using an explicit code, the explicit code definition takes precedence over the range definition for that code.