message: convert to mm for STL
diff: @@ -63,7 +63,7 @@ function getExporter(format: MakerJsPlaygroundExport.ExportFormat, result: Maker
  return makerjs.exporter.toOpenJsCad;
  case f.Stl:
  - function toStl(model: MakerJs.IModel, options: MakerJs.exporter.IOpenJsCadOptions) {
  + function toStl(model: MakerJs.IModel, inputOptions: MakerJs.exporter.IOpenJsCadOptions) {
  if (!deps[MakerJsPlaygroundExport.ExportFormat.Stl]) {
  importScripts(
  @@ -73,6 +73,15 @@ function getExporter(format: MakerJsPlaygroundExport.ExportFormat, result: Maker
  deps[MakerJsPlaygroundExport.ExportFormat.Stl] = true;
  }
  + //make sure size is in mm for STL
  + model = makerjs.model.convertUnits(model, makerjs.unitType.Millimeter);
  +
  + const defaultOptions: MakerJs.exporter.IOpenJsCadOptions = {
  + extrusion: 1
  + //TODO guesstimate a facet size
  + };
  + const options: MakerJs.exporter.IOpenJsCadOptions = makerjs.extendObject(defaultOptions, inputOptions);
  +
  const { CAG, CSG }: { CAG: typeof jscad.CAG, CSG: typeof jscad.CSG } = require('@jscad/csg');
  const stlSerializer: jscad.StlSerializer = require('@jscad/stl-serializer');
  @@ -163,7 +172,7 @@ onmessage = (ev: MessageEvent) => {
  try {
  result.text = exporter(request.model, request.options);
  } catch (e) {
  - result.error = e;
  + result.error = '' + e;
  }
  result.percentComplete = 100;
  postMessage(result);
  