function onChange(event) {
        if (self.options.imageUploadFunction) {
            self.uploadImagesUsingCustomFunction(self.options.imageUploadFunction, event.target.files);
        } else {
            self.uploadImages(event.target.files, onSuccess, onError);
        }
        imageInput.removeEventListener('change', onChange);
    }
Open the browse-file window to upload an image to a server.
@param [onSuccess] {function} see EasyMDE.prototype.uploadImage
@param [onError] {function} see EasyMDE.prototype.uploadImage