fix: enforce semantic commits in Renovate config (#205)

* Add Ethereum client and monitoring images to Renovate

Track all Docker images in docker-compose.yml and nimbus/Dockerfile:
- Nethermind, Lighthouse, Teku (docker-compose.yml)
- Nimbus eth2 + validator-client (nimbus/Dockerfile)
- Prometheus, Grafana (docker-compose.yml)

Groups: eth-clients, monitoring, charon (existing), github-actions (existing)

* fix: enforce semantic commits in Renovate config

Author: apham0001

.github/renovate.json

@@ -3,6 +3,7 @@
   "extends": [
     "config:recommended"
   ],
+  "semanticCommits": "enabled",
   "enabledManagers": [
     "github-actions",
     "regex"