Options.stylesheet does not accept `javascript`

[elmpp]

Hi there,

I'm seeing an error when trying to output javascript styles.

I have tried this with both gm and jimp compositors.

error message:

ENOENT: no such file or directory, open 'javascript'
error Command failed with exit code 1.

config:

{
    src: [path.resolve(__dirname, './assets/spriteable/horizontal/*')],
    spritePath: path.resolve(__dirname, 'assets/__generated__/spritesheet/allbookies-hz.png'),
    stylesheetPath: path.resolve(__dirname, 'assets/__generated__/spritesheet-style/allbookies-hz.js'),
    stylesheet: 'javascript',
    compositor: 'gm',
    compositorOptions: {
      compressionLevel: 6,
    },
  }

package.json:

{
  "name": "org-image",
  "version": "0.86.0",
  "description": "image processing stuff",
  "license": "ISC",
  "main": "lib/org-image.js",
  "scripts": {
    "build": "tsc",
    "postinstall": "cd ../.. && yarn postinstall",
    "postuninstall": "cd ../.. && yarn postinstall",
    "transpile": "npm run build",
    "transpile:watch": "npm run build -- --watch",
    "type-check": "tsc --noEmit"
  },
  "devDependencies": {
    "@types/node-sprite-generator": "^0.10.1",
    "node-sprite-generator": "^0.10.2",
    "ts-node": "8.2.0"
  },
  "bin": {
    "spritesheet": "scripts/spritesheet.sh"
  }
}