update slack icon to badgen
# IRedis (Interactive Redis)
[![CircleCI](https://circleci.com/gh/laixintao/iredis.svg?style=svg)](https://circleci.com/gh/laixintao/iredis)
[![PyPI version](https://badge.fury.io/py/iredis.svg)](https://badge.fury.io/py/iredis)
-[![Chat on slack](./docs/assets/chat-on-slack.svg)](https://join.slack.com/t/iredis/shared_invite/enQtNzQzMjkwOTI0MTE4LWFlNjQ4NzBlOTcyNmQ2MTQ4NGI2ODUxYTNhNTM5MmM4NjEyOTA4Y2VjNjQ1ZWQyNzMxYjY2M2E5N2U3ZDYxMTQ)
+[![Chat on slack](https://badgen.net/badge/icon/slack?icon=slack&label)](https://join.slack.com/t/iredis/shared_invite/enQtNzQzMjkwOTI0MTE4LWFlNjQ4NzBlOTcyNmQ2MTQ4NGI2ODUxYTNhNTM5MmM4NjEyOTA4Y2VjNjQ1ZWQyNzMxYjY2M2E5N2U3ZDYxMTQ)
[![Open in Cloud Shell](http://gstatic.com/cloudssh/images/open-btn.svg)](https://console.cloud.google.com/cloudshell/editor?cloudshell_git_repo=https://github.com/laixintao/iredis&cloudshell_print=docs/cloudshell/run-in-docker.txt)
