new mod: lr.com.layerfolders

[Malizma333]

Requires common.layers

Writes 3 bytes for every layer based on the count written by common.layers

The first byte is a boolean representing the layer type of the corresponding layer

• 1 for folder, 0 for layer

The next two bytes vary based on whether the layer is a folder or not

• Folder: u16 representing the size of the folder, which is the number of layers in the layer array before it that it encloses
• Layer: u16 representing the id of the folder containing it, or -1 (0xffff) for no folder