docs: add contact us info (#318)

README.md

@@ -17,6 +17,14 @@ BanyanDB, as an observability database, aims to ingest, analyze and store Metric
 
 The database research community usually uses [RUM conjecture](http://daslab.seas.harvard.edu/rum-conjecture/) to describe how a database access data. BanyanDB combines several access methods to build a comprehensive APM database to balance read cost, update cost, and memory overhead.
 
+## Contact us
+
+* Submit [an issue](https://github.com/apache/skywalking/issues/new) by selecting the [BanyanDB](https://github.com/apache/skywalking/issues?q=is%3Aopen+is%3Aissue+label%3Adatabase) component.
+* Mail list: **[email protected]**. Mail to [email protected], follow the reply to subscribe the mail list.
+* Send `Request to join SkyWalking slack` mail to the mail list(`[email protected]`), we will invite you in.
+* For Chinese speaker, send `[CN] Request to join SkyWalking slack` mail to the mail list(`[email protected]`), we will invite you in.
+* Twitter, [ASFSkyWalking](https://twitter.com/ASFSkyWalking)
+
 ## Documents
 
 [Documents](https://skywalking.apache.org/docs/skywalking-banyandb/next/readme/)