Add support for CVSS 4.0

[chandanbn]

Introduce an optional object type with cvssV4_0 field pointing to schema at https://www.first.org/cvss/cvss-v4.0.json

Likely target for 5.0.2 and before October end since this is a transparent change to CNAs.

[david-waltermire]

Will assign to @fjscao. He committed to submit a PR by 10/8/2023.

[sei-vsarvepalli]

Looks like the https://www.first.org/cvss/cvss-v4.0.json has an error Line 125 should be "multipleOf" instead of "multiple" - I am also writing to let the CVSS SIG know about it.
Line 121-126

        "scoreType": {
            "type": "number",
            "minimum": 0,
            "maximum": 10,
            "multiple": 0.1
        },

should be multipleOf from https://json-schema.org/understanding-json-schema/reference/numeric.html#multiples

        "scoreType": {
            "type": "number",
            "minimum": 0,
            "maximum": 10,
            "multipleOf": 0.1
        },

[sei-vsarvepalli]

FIRST has released a new version at https://www.first.org/cvss/cvss-v4.0.json dated October 2, 2023

  "$id": "https://www.first.org/cvss/cvss-v4.0.json?20231002"

The CVSSv4 JSON schema error has been resolved.

[fjscao]

pull request was created on Oct. 5: #253

The other possible changes were discussed with Chandan and Dave in email.

[chandanbn]

addressed in 5.1.0