Fix README table alignment (#484)

README.md

@@ -235,7 +235,7 @@ Auth0
 You can make users land directly on the Signup page instead of the Login page by specifying the `"screen_hint": "signup"` parameter when performing Web Authentication. Note that this can be combined with `"prompt": "login"`, which indicates whether you want to always show the authentication page or you want to skip if there's an existing session.
 
 | Parameters                                     | No existing session   | Existing session              |
-|:----------------------------------------------:|:---------------------:|:-----------------------------:|
+|:-----------------------------------------------|:----------------------|:------------------------------|
 | no extra parameters                            | Shows the login page  | Redirects to the callback url |
 | `"screen_hint": "signup"`                      | Shows the signup page | Redirects to the callback url |
 | `"prompt": "login"`                            | Shows the login page  | Shows the login page          |