add getCustomerId to the interface (#19)

* add getCustomerId to the interface

Author: art333

src/ps-web-apis.ts

@@ -83,6 +83,11 @@ export interface WhoamiV1 {
      * @return {WhoamiUserInfo} some relevant userdata
      */
     getUserInfo(): Promise<WhoamiUserInfo>;
+    /**
+     * will request customer pseudo id for currently logged user from consent backend
+     * @param clientId The string identifier of the client for which the customer id is requested.
+     */
+    getCustomerId(clientId: string): Promise<string>;
 }
 
 export function whoamiV1(): Promise<WhoamiV1> {