IPv4 Format not correctly supporting CIDR notations

[dgmorrisjr]

Per the documentation here (https://json-schema.org/understanding-json-schema/reference/type), the "ipv4": IPv4 address, according to dotted-quad ABNF syntax as defined in [RFC 2673, section 3.2](http://tools.ietf.org/html/rfc2673#section-3.2)

Reading the RFC spec: "The <bit-spec> is either a dotted quad or a base indicator and a
sequence of digits appropriate to that base, optionally followed by a slash and a length." indicates a CIDR range?

currently the python library is failing validation on CIDRs when using the ipv4 format constraint.

[gregsdennis]

This is something to raise in the library's repository. This repository is for the JSON Schema implementation itself and has no association with any implementation.

[jdesrosiers]

The ipv4 format uses the "dotted-quad" ABNF production, which doesn't include CIDRs.

dotted-quad = decbyte "." decbyte "." decbyte "." decbyte
decbyte = 1*3DIGIT