Add 'social_csrf_token' cookie info (#57641)

Co-authored-by: Felicity Chapman <felicitymay@github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>

Author: 4 people

content/site-policy/privacy-policies/github-cookies.md

@@ -46,6 +46,7 @@ GitHub | `saml_csrf_token_legacy` | This cookie is set by SAML auth path method
 GitHub | `saml_return_to` | This cookie is set by the SAML auth path method to maintain state during the SAML authentication loop. | Until user closes browser or completes authentication request
 GitHub | `saml_return_to_legacy` | This cookie is set by the SAML auth path method to maintain state during the SAML authentication loop. | Until user closes browser or completes authentication request
 GitHub | `show_cookie_banner` | Set based on the client’s region and used to determine if a cookie consent banner should be shown | Session
+GitHub | `social_csrf_token` | This cookie is set by the social initiate path to ensure that the user that started the flow is the same user that completes it. | 5 minutes
 GitHub | `tz` | This cookie allows us to customize timestamps to your time zone. | Session
 GitHub | `user_session` | This cookie is used to log you in. | Two weeks
 [Microsoft](https://privacy.microsoft.com/en-us/privacystatement) | `ai_session` | Application Insights session ID | One year