CODEOWNERS: Add codeowners for loki operator (grafana#10222)

**What this PR does / why we need it**:
Explicit code-owners for loki operator

**Which issue(s) this PR fixes**:
Fixes #<issue number>

**Special notes for your reviewer**:

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

CODEOWNERS

@@ -4,5 +4,8 @@
 # Documentation.
 /docs/ @grafana/docs-logs @grafana/loki-team
 
+# Loki operator
+/operator/ @grafana/loki-team @periklis @xperimental
+
 # No owners - allows sub-maintainers to merge changes.
 CHANGELOG.md