Enhancement: Add support for choice fields with ID and Title

[estruyf]

To have a more dynamic approach for setting choice field values and update these in the site generation process, it would be nice to have support for ID and Title.

{
          "title": "Multi-select with ID",
          "name": "choiceId",
          "type": "choice",
          "choices": [
            { "id": 1, "title": "Choice 1" },
            { "id": "2", "title": "Choice 2" },
            { "id": "3", "title": "Choice 3" }
          ],
          "multiSelect": true 
}

The user can choose if they want to use a string or { id: string; title: string} object.