Update OWNERS

This PR creates a new group "cluster-api-operator-maintainers" to
distinguish project maintainers from admins.

Also for numerous quality improvements we add furkatgofurov7 as a
project maintainer.

Author: Fedosin

OWNERS

@@ -4,3 +4,4 @@
 approvers:
   - sig-cluster-lifecycle-leads
   - cluster-api-operator-admins
+  - cluster-api-operator-maintainers

OWNERS_ALIASES

@@ -18,3 +18,11 @@ aliases:
   - Fedosin
   - alexander-demicev
   - damdo
+
+  # non-admin folks who have write-access and can approve any PRs in the repo
+  cluster-api-operator-maintainers:
+  - JoelSpeed
+  - Fedosin
+  - alexander-demicev
+  - damdo
+  - furkatgofurov7