Add archive note (#26)

* Add archive note

* Update README.md

Co-authored-by: 吴晟 Wu Sheng <wu.sheng@foxmail.com>
diff --git a/README.md b/README.md
index 3e46539..e5339c3 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,10 @@
+# This repo is archived
+
+Since SkyWalking 8.8.0, the Dockerfiles are merged
+into [the OAP repo](https://github.com/apache/skywalking/tree/master/docker)
+and [the Java agent repo](https://github.com/apache/skywalking-java) respectively, this repo is archived and not
+maintained anymore.
+
 # Apache SkyWalking Docker Files
 
 <img src="http://skywalking.apache.org/assets/logo.svg" alt="Sky Walking logo" height="90px" align="right" />