fix(fs): replace fs imports with locally defined WriteStream interface

src/types/WriteStream.ts

@@ -0,0 +1,4 @@
+export interface WriteStream {
+  write: (content: string, callback: (err?: Error) => any) => void
+  path: string
+}

src/types/index.ts

@@ -11,3 +11,4 @@ export * from './SASjsRequest'
 export * from './Session'
 export * from './UploadFile'
 export * from './PollOptions'
+export * from './WriteStream'