Document `cards` field of `notesInfo`

[louwers]

notesInfo returns a field cards.

This should be documented.

Right now, this is what the docs says:

{
    "result": [
        {
            "noteId":1502298033753,
            "modelName": "Basic",
            "tags":["tag","another_tag"],
            "fields": {
                "Front": {"value": "front content", "order": 0},
                "Back": {"value": "back content", "order": 1}
            }
        }
    ],
    "error": null
}