Free the getResponseBody

[maertz]

Is your feature request related to a problem? Please describe.
I'm not able to overwrite the getResponseBody method in my uploaderClass which extends the "Uploader" class.

Describe the solution you'd like
Make getResponseBody public to be able to take full control over the response body parsing on uploader class level.

Describe alternatives you've considered
Handle such behaviour on upload item level (not prefered) :)

Additional context
I've used the MultiPartFormData example within the "upload-examples" to demonstrate this.

export class MultiPartFormData extends Uploader {
  responseType = 'json' as XMLHttpRequestResponseType;

  private getResponseBody(xhr: any) { 
    let body: UploadAttachmentFilesResponse[] =
      'response' in xhr ? xhr.response : xhr.responseText;
    if (body && this.responseType === 'json' && typeof body === 'string') {
      try {
        body = JSON.parse(body);
      } catch (_a) {}
    }

    return body
  }

  async getFileUrl(): Promise<string> {
    this.offset = 0;
    const formData: FormData = new FormData();
    formData.append('files', this.file, this.file.name);
    await this.request({
      method: 'POST',
      body: formData,
      url: this.endpoint,
      progress: true
    });
    this.offset = this.size;
    const location = this.getValueFromResponse('location');
    return location ? resolveUrl(location, this.endpoint) : '';
  }

  async sendFileContent(): Promise<number | undefined> {
    return this.size;
  }

  async getOffset(): Promise<number | undefined> {
    return 0;
  }
}

Cheers :)