fix(secure-storage): add missing function (#1626)

* fix(secure-storage): add missing function

fix #1625

* Update index.ts

src/@ionic-native/plugins/secure-storage/index.ts

@@ -57,6 +57,13 @@ export class SecureStorageObject {
   })
   clear(): Promise<any> { return; }
 
+  /**
+   * Brings up the screen-lock settings
+   * @returns {Promise<any>}
+   */
+  @CordovaInstance()
+  secureDevice(): Promise<any> { return; }
+
 }
 
 /**