added namespace to VaultOptions (#162)

Co-authored-by: Krispin Schulz <krispinone@googlemail.com>

Author: kstiehl

index.d.ts

@@ -120,6 +120,7 @@ declare namespace NodeVault {
 
         apiVersion?: string;
         endpoint?: string;
+        namespace?: string;
         noCustomHTTPVerbs?: boolean;
         pathPrefix?: string;
         token?: string;