Add title & description to union Case _s

[smondet]

The title and description then show up properly in generated schemas, e.g.:

      "oneOf": [
        {
          "title": "inline-markdown",
          "description": "Markdown prose as a string.",
          "type": "object",
          "properties": {
            "inline-markdown": {
              "$ref": "#/definitions/unistring"
            }
          },
          "required": [
            "inline-markdown"
          ],
          "additionalProperties": false
        },
        {
          "title": "external",
          "description": "URI referencing Markdown prose in another document.",
          "type": "object",
          "properties": {
            "external": {
              "$ref": "#/definitions/unistring"
            }
          },
          "required": [
            "external"
          ],
          "additionalProperties": false
        }
      ]

[raphael-proust]

This is over by https://gitlab.com/nomadic-labs/json-data-encoding/merge_requests/1

[smondet]

https://gitlab.com/nomadic-labs/json-data-encoding/merge_requests/1 was merged and release is in progress 🎉