Request: traversing into enum for failure message

[jamesbraza]

In astral-sh/ruff#11880 today with validate-pyproject==0.18, I am getting an error that says:

[ERROR] `tool.ruff.lint` cannot be validated by any definition:

The actual error was in an extend-select field whose JSON schema type is enum:

    "RuleSelector": {
      "type": "string",
      "enum": [
        "A",
        "A0",
        ...,
      ]
    },

The request here is to traverse into the enum for a better error message:

[ERROR] `tool.ruff.lint.extend-select` cannot be validated by any definition:

To show where the exact error lies