code: function makeBaseStackupLayer(layer) {
      var layerSide = layer.side
      var layerType = layer.type
  
      if (
        layer.filename &&
        typeof layerSide === 'undefined' &&
        typeof layerType === 'undefined'
      ) {
        var gerberId = layerTypes[layer.filename]
        layerSide = gerberId.side
        layerType = gerberId.type
      }
  
      var layerOptions = extend(layer.options)
  
      if (layerOptions.plotAsOutline == null && layerType === wtg.TYPE_OUTLINE) {
        layerOptions.plotAsOutline = true
      }
  
      if (
        options &&
        options.outlineGapFill != null &&
        layerOptions.plotAsOutline
      ) {
        layerOptions.plotAsOutline = options.outlineGapFill
      }
  
      return extend(layer, {
        side: layerSide,
        type: layerType,
        options: layerOptions,
      })
    }
docs: extend pcb-stackup input layer with necessary details for pcb-stackup-core