limit PR to 400 LOC

.github/pull_request_template.md

@@ -6,6 +6,7 @@
 - [ ] Code has been linted and run through `cargo fmt`.
 - [ ] If any new functionality has been added, unit tests were also added.
 - [ ] [CONTRIBUTING.md](https://github.com/EFForg/rayhunter/blob/main/CONTRIBUTING.md) has been read.
+- [ ] Your pull request is fewer than ~400 lines of code.
 
 You must check one of:
 - [ ] No generative AI (including LLMs) tools were used to create this PR.

CONTRIBUTING.md

@@ -58,6 +58,8 @@ Otherwise:
   manually test them. Our test coverage isn't great, but as new features are
   added we are trying to prevent it from becoming worse.
 
+- Please keep your contirbutions to less than approximately 400 lines of code (going slightly over is fine, we aren't dogmatic about it.) This is because we are not able to give quality code review to contributions larger than that and risk introducing bugs into the system. [There was a study showing 400 LOC is the max most humans can handle.](https://smartbear.com/learn/code-review/best-practices-for-peer-code-review/)
+
 If you have any questions [feel free to open a discussion or chat with us on Mattermost.](https://efforg.github.io/rayhunter/support-feedback-community.html)
 
 ### Policy regarding AI-generated contributions: