Add missing type definition (#677)

* Add type definition for download_folder function

Author: vin-krish

types/cloudinary_ts_spec.ts

@@ -911,6 +911,16 @@ cloudinary.v2.utils.download_zip_url(
     }
 );
 
+// $ExpectType string
+cloudinary.v2.utils.download_folder(
+    'my-folder',
+    {
+        resource_type: 'image',
+        prefixes: 'photos/'
+    }
+);
+
+
 // $ExpectType { [key: string]: any; signature: string; api_key: string; }
 cloudinary.v2.utils.sign_request(
     {}

types/index.d.ts

@@ -924,6 +924,8 @@ declare module 'cloudinary' {
 
             function download_zip_url(options?: ArchiveApiOptions | ConfigAndUrlOptions): string;
 
+            function download_folder(folder_path: string, options?: ArchiveApiOptions | ConfigAndUrlOptions): string;
+
             function download_backedup_asset(asset_id?: string, version_id?: string, options?: ArchiveApiOptions | ConfigAndUrlOptions): string
 
             function generate_auth_token(options?: AuthTokenApiOptions): string;