itch.io

That's just a macos folder. it's a script not an extension - drop it in your scripts folder, don't try to install as extension.

If anyone runs into the nil value error, update this function in the .lua file with this:

local function newLayer(name)
  local s = app.activeSprite
  local lyr = s:newLayer()
  lyr.name = name
  local img = Image(s.spec)
  local cel = s:newCel(lyr, app.activeFrame.frameNumber, img, Point(0, 0))
  app.activeLayer = lyr
  app.activeCel = cel
  return lyr
end