fix: typo in documentation (#187)

Author: mkonikov

README.md

@@ -28,7 +28,7 @@ encrypting it, or use a server-side session instead.
 
 **NOTE** This module does not prevent session replay, as the expiration set is that
 of the cookie only; if that is a concern of your application, you can store an expiration
-date in `req.session` object and validate it on the sever, and implement any other logic
+date in `req.session` object and validate it on the server, and implement any other logic
 to extend the session as your application needs.
 
 ## Install