PR template: add checkbox for new unsafe code
Remind authors and reviewers to carefully audit unsafe code.
@@ -29,3 +29,5 @@ the terms of the Apache 2.0 license.
reflected in `firecracker/swagger.yaml`.
- [ ] Either the changes in this PR have no user impact, or, the changes in
this PR have user impact and have been added to the `CHANGELOG.md` file.
+- [ ] Either no new `unsafe` code has been added, or, the newly added `unsafe`
+ code is unavoidable and properly documented.
