Add freezes and restrictions to pr guidelines (#270)

src/en/general-development/codebase-info/pull-request-guidelines.md

@@ -10,6 +10,8 @@ Thank you for contributing to Space Station 14. When submitting pull requests (P
 
 - Large new features and comprehensive reworks to existing large features (ie antags or anything that could be considered a subdepartment unto itself), should first be [proposed and accepted in abstract](../feature-proposals.md) before you start working on actually implementing it.
 
+- Read the [Freezes and Restrictions issue](https://github.com/space-wizards/space-station-14/issues/8524) and make sure your PR does not interfere with anything or requires special requirements.
+
 ## Content
 
 - **Make separate PRs for feature changes, bug fixes, and cleanup/refactors.** This makes changes easier to review, reduces conflicts, and also easier to revert if something goes wrong.