Update the link of the slack channel and GitHub address (#887)

* [update] update some links in readme
Signed-off-by: BellaXiang <42797797+BellaXiang@users.noreply.github.com>

website/blog/2020-03-18-run-your-first-chaos-experiment.md

@@ -186,7 +186,7 @@ kind delete cluster --name=kind
 
 Congratulations on your first successful journey into Chaos Engineering. How does it feel? Chaos Engineering is easy, right? But perhaps Chaos Mesh is not that easy-to-use. Command-line operation is inconvenient, writing YAML files manually is a bit tedious, or checking the experiment results is somewhat clumsy? Don't worry, Chaos Dashboard is on its way! Running chaos experiments on the web sure does sound exciting! If you'd like to help us build testing standards for cloud platforms or make Chaos Mesh better, we'd love to hear from you!
 
-If you find a bug or think something is missing, feel free to file an issue, open a pull request (PR), or join us on the #sig-chaos-mesh channel in the [TiDB Community](https://chaos-mesh.org/tidbslack) slack workspace.
+If you find a bug or think something is missing, feel free to file an issue, open a pull request (PR), or join us on the #project-chaos-mesh channel in the [CNCF slack workspace](https://join.slack.com/t/cloud-native/shared_invite/zt-fyy3b8up-qHeDNVqbz1j8HDY6g1cY4w).
 
 GitHub: [https://github.com/chaos-mesh/chaos-mesh](https://github.com/chaos-mesh/chaos-mesh)