chore(ci) add area/gateway label (#3263)

Signed-off-by: James Peach <james.peach@konghq.com>
(cherry picked from commit 40260e2)

# Conflicts:
#	labels.yml

labels.yml

@@ -0,0 +1,39 @@
+default:
+  labels:
+    - color: 5319e7
+      name: "backport-to-stable"
+      description: "Automatically backport this PR to the latest stable branch"
+    - color: 0052cc
+      name: "area/kuma-cp"
+    - color: 0052cc
+      name: "area/kuma-dp"
+    - color: 0052cc
+      name: "area/kumactl"
+    - color: 0052cc
+      name: "area/k8s"
+    - color: 0052cc
+      name: "area/universal"
+    - color: 0052cc
+      name: "area/observability"
+    - color: 0052cc
+      name: "area/dns"
+    - color: 0052cc
+      name: "area/multizone"
+    - color: 0052cc
+      name: "area/api"
+    - color: 0052cc
+      name: "area/policies"
+    - color: 0052cc
+      name: "area/ci-cd"
+    - color: 0052cc
+      name: "area/performance"
+    - color: 0052cc
+      name: "area/installation"
+    - color: 0052cc
+      name: "area/envoy"
+    - color: 0052cc
+      name: "area/adoption"
+      description: "Likely to cause problem to new comers"
+    - color: 0052cc
+      name: "area/gateway"
+      description: "Built-in Kuma gateway support"