It used an old vendored version of acorn.js which seems to choke on this
trailing comma. This is not a problem for more recent Emscripten versions.
We disable the `comma-dangle` check in ESLint to prevent this issue.
Applies to javascript files inside the platform library folder, the
exposed Engine code, and any javascript files in modules.
Files ending with ".externs.js" will be ignored, you can create a
".eslintignore" file to specify extra files to be ignored.