feat: add openim images config path

Signed-off-by: Xinwei Xiong(cubxxw) <3293172751nss@gmail.com>

pkg/common/metrics/grpc_msggateway.go

@@ -0,0 +1,12 @@
+package prom_metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	OnlineUserGauge = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "online_user_num",
+		Help: "The number of online user num",
+	})
+)