[docs] Add code review instructions to repository

Added guidelines for code review focusing on security, performance, and code quality.

Author: SamuelHassine

.github/instructions/code-review.instructions.md

@@ -0,0 +1,46 @@
+---
+applyTo: "**/*"
+---
+
+When reviewing code, focus on:
+
+## Security Critical Issues
+- Check for hardcoded secrets, API keys, or credentials
+- Look for SQL injection and XSS vulnerabilities
+- Verify proper input validation and sanitization
+- Review authentication and authorization logic
+
+## Performance Red Flags
+- Identify N+1 database query problems
+- Spot inefficient loops and algorithmic issues
+- Check for memory leaks and resource cleanup
+- Review caching opportunities for expensive operations
+
+## Code Quality Essentials
+- Functions should be focused and appropriately sized
+- Use clear, descriptive naming conventions
+- Ensure proper error handling throughout
+
+## Review Style
+- Be specific and actionable in feedback
+- Explain the "why" behind recommendations
+- Acknowledge good patterns when you see them
+- Ask clarifying questions when code intent is unclear
+
+Always prioritize security vulnerabilities and performance issues that could impact users.
+
+Always suggest changes to improve readability. For example, this suggestion seeks to make the code more readable and also makes the validation logic reusable and testable.
+
+// Instead of:
+if (user.email && user.email.includes('@') && user.email.length > 5) {
+  submitButton.enabled = true;
+} else {
+  submitButton.enabled = false;
+}
+
+// Consider:
+function isValidEmail(email) {
+  return email && email.includes('@') && email.length > 5;
+}
+
+submitButton.enabled = isValidEmail(user.email);