Add security considerations section to PR template (#5530)

Added a section for security considerations in the PR template.

Author: bartaz

.github/pull_request_template.md

@@ -6,6 +6,17 @@
 - [ ] This PR has tests
 - [ ] No testing required (explain why):
 
+## Security
+
+- [ ] Security considerations for review (list them):
+  - [ ] Examples:
+  - [ ] Access control: users can only access their own data
+  - [ ] Input: user input is validated and sanitised
+  - [ ] Sensitive data: secret or private data is not exposed in any way
+  - [ ] ...
+- [ ] This PR has no security considerations (explain why):
+
+
 ## Issue / Card
 Fixes #