Add AltinityDB Slack badge to README.

ReadMe.md

@@ -7,6 +7,9 @@
 [![Docker Image](https://img.shields.io/docker/pulls/altinity/clickhouse-backup.svg)](https://hub.docker.com/r/altinity/clickhouse-backup)
 [![Downloads](https://img.shields.io/github/downloads/Altinity/clickhouse-backup/total.svg)](http://github.com/Altinity/clickhouse-backup/releases)
 [![Coverage Status](https://coveralls.io/repos/github/Altinity/clickhouse-backup/badge.svg)](https://coveralls.io/github/Altinity/clickhouse-backup)
+<a href="https://altinity.com/slack">
+  <img src="https://img.shields.io/static/v1?logo=slack&logoColor=959DA5&label=Slack&labelColor=333a41&message=join%20conversation&color=3AC358" alt="AltinityDB Slack" />
+</a>
 
 A tool for easy backup and restore utility for ClickHouse databases with support for many cloud and non-cloud storage types.
 
@@ -39,7 +42,7 @@ services related to ClickHouse.
 - [Official website](https://altinity.com/) - Get a high level overview of Altinity and our offerings.
 - [Altinity.Cloud](https://altinity.com/cloud-database/) - Run ClickHouse in our cloud or yours.
 - [Altinity Support](https://altinity.com/support/) - Get Enterprise-class support for ClickHouse.
-- [Slack](https://altinitydbworkspace.slack.com/join/shared_invite/zt-1togw9b4g-N0ZOXQyEyPCBh_7IEHUjdw#/shared-invite/email) - Talk directly with ClickHouse users and Altinity devs.
+- [Slack](https://altinity.com/slack) - Talk directly with ClickHouse users and Altinity devs.
 - [Contact us](https://hubs.la/Q020sH3Z0) - Contact Altinity with your questions or issues.
 - [Free consultation](https://hubs.la/Q020sHkv0) - Get a free consultation with a ClickHouse expert today.