Fix SAMESITE documentation - closes #647

https://docs.djangoproject.com/en/5.1/ref/settings/#std-setting-SESSION_COOKIE_SAMESITE

README.md

@@ -123,7 +123,7 @@ applications `settings.py` to make use of cookies:
 
 ```python
 SESSION_ENGINE = "django.contrib.sessions.backends.signed_cookies"
-SESSION_COOKIE_SAMESITE = None
+SESSION_COOKIE_SAMESITE = 'None'
 SESSION_COOKIE_SECURE = True
 ```