[Feat.] Enable grafana to show metrics (#4718)

Co-authored-by: zhaochenyang20 <zhaochen20@outlook.com>

examples/monitoring/grafana/dashboards/config/dashboard.yaml

@@ -0,0 +1,11 @@
+apiVersion: 1
+providers:
+  - name: 'SGLang'
+    orgId: 1
+    folder: 'SGLang Monitoring'
+    type: file
+    disableDeletion: false
+    updateIntervalSeconds: 10
+    allowUiUpdates: false
+    options:
+      path: /var/lib/grafana/dashboards