Update docker-compose.yml to use 2.2 tag

alexcheng1982 · alexcheng1982 · commit c60f0e2e6329 · 2018-12-06T08:35:40.000+13:00
diff --git a/docker-compose.yml b/docker-compose.yml
@@ -1,7 +1,7 @@
 version: '3.0'
 services:
   web:
-    image: alexcheng/magento2
+    image: alexcheng/magento2:2.2
     ports:
       - "80:80"
     links:
