deployment/docker/docker-compose: expose port for vminsert (#3096)

deployment/docker: open port for vminsert because it can't be reached from nginx/curl/etc as it run at random port in OS

deployment/docker/README.md

@@ -9,8 +9,8 @@ For single version check [docker compose in master branch](https://github.com/Vi
 ## VictoriaMetrics
 
 VictoriaMetrics cluster in this environment consists of 
-vminsert, vmstorage and vmselect components. Only vmselect
-has exposed port `:8481` and the rest of components are available
+vminsert, vmstorage and vmselect components. vmselect
+has exposed port `:8481`, vminsert has exposed port `:8480` and the rest of components are available
 only inside of environment. 
 The communication scheme between components is the following:
 * [vmagent](#vmagent) sends scraped metrics to vminsert;

deployment/docker/docker-compose.yml

@@ -64,7 +64,7 @@ services:
       - '--storageNode=vmstorage-1:8400'
       - '--storageNode=vmstorage-2:8400'
     ports:
-      - 8480
+      - 8480:8480
     restart: always
   vmselect:
     container_name: vmselect