Support for repeated slots.

[Lattyware]

Massive Decks already supports this via an optional index parameter on slots, so if we can produce it, it'll work, e.g:

  calls: [
    [
      ["Steve Ballmer:"],
      [
        "“",
        { "transform": "UpperCase" },
        ", ",
        { "transform": "UpperCase", "index": 0 },
        ", ",
        { "transform": "UpperCase", "index": 0 },
        ".”",
      ],
    ],
  ],
  responses: [
    "developers",
  ]

The question is how to integrate this nicely into the editor experience.