Fix d.ts for multipart options.

Author: Palid

index.d.ts

@@ -93,6 +93,8 @@ declare module "react-native-background-upload" {
          * in the context of ShareExtension.
          */
         appGroup?: string;
+        // Necessary only for multipart type upload
+        field?: string
     }
 
     export interface MultipartUploadOptions extends UploadOptions {
@@ -108,7 +110,7 @@ declare module "react-native-background-upload" {
     export type UploadListenerEvent = 'progress' | 'error' | 'completed' | 'cancelled'
 
     export default class Upload {
-        static startUpload(options: UploadOptions): Promise<uploadId>
+        static startUpload(options: UploadOptions | MultipartUploadOptions): Promise<uploadId>
         static addListener(event: UploadListenerEvent, uploadId: uploadId, data: object): void
         static addListener(event: 'progress', uploadId: uploadId, data: ProgressData): void
         static addListener(event: 'error', uploadId: uploadId, data: ErrorData): void