chore(common): update code owners

Author: antoniupop

.github/CODEOWNERS

@@ -20,6 +20,7 @@ test-suite/gateway-stress/Dockerfile @zama-ai/fhevm-devs
 # Coprocessor Team ownership
 /coprocessor/ @zama-ai/fhevm-coprocessor
 /host-contracts/ @zama-ai/fhevm-coprocessor
+/library-solidity/ @zama-ai/fhevm-coprocessor
 
 # Enforces changes in Sandboxed AI CI/CD
 .github/squid/sandbox-*.conf @zama-ai/security-team