Add Grafana provisioning files for dashboards and datasources

- Introduced a new dashboard configuration file for the Node Exporter Full dashboard.
- Added provisioning for Grafana dashboards in main.yml.
- Configured Prometheus as the default datasource in main.yml.

grafana/provisioning/dashboards/main.yml

@@ -0,0 +1,11 @@
+apiVersion: 1
+
+providers:
+  - name: "default"
+    orgId: 1
+    folder: ""
+    type: file
+    disableDeletion: false
+    editable: true
+    options:
+      path: /var/lib/grafana/dashboards

grafana/provisioning/datasources/main.yml

@@ -0,0 +1,11 @@
+apiVersion: 1
+
+datasources:
+  - name: Prometheus
+    type: prometheus
+    access: proxy
+    url: http://prometheus:9090
+    isDefault: true
+    jsonData:
+      timeInterval: 15s
+    editable: true