Add sig-architecture-approvers and dep-approvers to root dir

OWNERS

@@ -2,8 +2,12 @@
 
 filters:
   ".*":
-    reviewers: []
-    approvers: []
+    reviewers:
+      - dep-reviewers
+      - sig-architecture-approvers
+    approvers:
+      - dep-approvers # for go.mod/go.sum
+      - sig-architecture-approvers # for OWNERS_ALIASES and other root files
     emeritus_approvers:
       - bgrant0607
       - brendandburns

OWNERS_ALIASES

@@ -1,4 +1,6 @@
 aliases:
+  # Note: sig-architecture-approvers has approval on root files (including go.mod/go.sum) until https://github.com/kubernetes/test-infra/pull/21398 is resolved.
+  # People with approve rights via this alias should defer dependency update PRs to dep-approvers.
   sig-architecture-approvers:
     - dims
     - derekwaynecarr
@@ -462,6 +464,8 @@ aliases:
     - jayunit100
     - jsturtevant
     - marosset
+  # Note: dep-approvers has approval on root files (including OWNERS_ALIASES) until https://github.com/kubernetes/test-infra/pull/21398 is resolved.
+  # People with approve rights via this alias should defer updates of root files other than go.mod/go.sum to dep-approvers.
   dep-approvers:
     - BenTheElder
     - cblecker