r/vmalert: Deploy vmalert

`vmalert` is a component of Victoria Metrics. It handles alerting and
recording rules, periodically executing queries and dispatching alerts
or writing aggregated data back to the TSDB.

roles/vmalert/handlers/main.yml

@@ -0,0 +1,9 @@
+- name: restart vmalert
+  service:
+    name: vmalert
+    state: restarted
+
+- name: reload vmalert
+  uri:
+    url: http://[::1]:8880/-/reload
+  changed_when: true