fix: request body type (#129)

Fixes two problems:

1. The import for `NodeReadableStream` was missing
2. We can't use `NodeReadableStream` as the type for `body` because it it not assignable
    to any type that makes up `BodyInit` so instead [modify](https://stackoverflow.com/questions/41285211/overriding-interface-property-type-defined-in-typescript-d-ts-file)
    the RequestInit type to omit the original `body` type and include the new one.

Co-authored-by: Irakli Gozalishvili <[email protected]>

src/types.d.ts

@@ -1,3 +1,5 @@
+import { Readable as NodeReadableStream } from 'stream'
+
 interface ProgressStatus {
   total: number
   loaded: number
@@ -6,7 +8,9 @@ interface ProgressStatus {
 
 export interface ProgressFn { (status: ProgressStatus): void }
 
-export interface FetchOptions extends RequestInit {
+type Override<T, R> = Omit<T, keyof R> & R
+
+export type FetchOptions = Override<RequestInit, {
   /**
    * Extended body with support for node readable stream
    */
@@ -29,7 +33,7 @@ export interface FetchOptions extends RequestInit {
    */
   onDownloadProgress?: ProgressFn
   overrideMimeType?: string
-}
+}>
 
 export interface HTTPOptions extends FetchOptions {
   json?: any