jhatwich/layer comps+size

To use this feature add a layer comp and name it something like "overview.png" or "200% overview.png"
I don't completely understand this, but I'm concerned about this. The DOM does not explicitly represent layer indices from Photoshop very intentionally. Instead, indices are derived from the current layer structure. The intent was to make it simpler to keep them up to date. I could very well be wrong, but it doesn't look the `_index` property is ever being updated after layer creation, and so as soon as the layers are reordered all the indices will be incorrect.