fix(core): document image values in .env (#282)

Author: dsx137

.env

@@ -15,10 +15,10 @@ NODE_EXPORTER_IMAGE=prom/node-exporter:v1.7.0 # Prometheus Node Exporter image v
 
 # OpenIM server and chat service images
 OPENIM_SERVER_IMAGE=openim/openim-server:v3.8.3-patch.12 # OpenIM server application image version
-#OPENIM_SERVER_IMAGE=registry.cn-hangzhou.aliyuncs.com/openimsdk/openim-server:release-v3.8.3
+#OPENIM_SERVER_IMAGE=registry.cn-hangzhou.aliyuncs.com/openimsdk/openim-server:release-v3.8.3 # should be the same as above
 
 OPENIM_CHAT_IMAGE=openim/openim-chat:v1.8.4-patch.2 # OpenIM chat application image version
-#OPENIM_CHAT_IMAGE=registry.cn-hangzhou.aliyuncs.com/openimsdk/openim-chat:release-v1.8.4
+#OPENIM_CHAT_IMAGE=registry.cn-hangzhou.aliyuncs.com/openimsdk/openim-chat:release-v1.8.4 # should be the same as above
 
 
 # Directory for data storage