Add ability to show single page while in 2 page mode

If a page exists that is larger than the other pages show it as a single page spread across left and right.

```javascript
"data": [
[
{
"width": 612,
"height": 792,
"type": "cover",
"uri": "./1.png"
}
],
[
{
"width": 612,
"height": 792,
"type": "left",
"uri": "./2.png"
},
{
"width": 612,
"height": 792,
"type": "right",
"uri": "./3.png"
}
],
[
{
"width": 612,
"height": 792,
"type": "left",
"uri": "./4.png"
},
{
"width": 612,
"height": 792,
"type": "right",
"uri": "./5.png"
}
],
[
{
"width": 1224,
"height": 792,
"type": "spread",
"uri": "./6.png"
}
],
[
{
"width": 612,
"height": 792,
"type": "left",
"uri": "./7.png"
},
{
"width": 612,
"height": 792,
"type": "right",
"uri": "./8.png"
}
]
],`
```

How this is currently done
![example]

[example]: https://i.imgur.com/O0CqWew.png