Typescript types for the newly-announced R2 worker bindings for multipart uploads.
// https://github.com/cloudflare/workerd/blob/main/src/workerd/api/r2-bucket.h
export interface R2BucketWithMultipart extends R2Bucket {
createMultipartUpload(key: string, opts?: R2MultipartOptions): Promise<R2MultipartUpload>;
resumeMultipartUpload(key: string, uploadId: string): Promise<R2MultipartUpload>;
}
export interface R2MultipartOptions {