Fix Slack references

Author: oleg-nenashev

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 # Contributing to the Site
 
-[![Slack: GradleUp on the Gradle Community Slack](https://img.shields.io/badge/Slack-%23hacktoberfest-brightgreen?style=flat&logo=slack)](./docs/community/participate.md#slack)
+[![Slack: GradleUp on the Gradle Community Slack](https://img.shields.io/badge/Slack-%23gradleup-brightgreen?style=flat&logo=slack)](./docs/community/participate.md#slack)
 
 Any contributions, typo fixes and patches are welcome!
 The content is located inside this repository and in the

README.md

@@ -4,7 +4,7 @@
 
 [![Website](https://img.shields.io/static/v1?label=Website&message=gradleup.com&color=blue)](https://gradleup.com/)
 [![Docs](https://img.shields.io/static/v1?label=Projects&message=10%2b&color=green)](https://gradleup.com/projects/)
-[![Slack: GradleUp on the Gradle Community Slack](https://img.shields.io/badge/Slack-%23hacktoberfest-brightgreen?style=flat&logo=slack)](./docs/community/participate.md#slack)
+[![Slack: GradleUp on the Gradle Community Slack](https://img.shields.io/badge/Slack-%23gradleup-brightgreen?style=flat&logo=slack)](https://gradleup.com/docs/community/participate/#slack)
 [![Participate](https://img.shields.io/static/v1?label=Contributor&message=Guide&color=lightgreen)](https://gradleup.com/docs/community/participate/)
 
 This repository hosts a [GradleUp website](https://gradleup.com/).

docs/community/participate.md

@@ -1,5 +1,7 @@
 # GradleUp Community Channels
 
+[![Slack: GradleUp on the Gradle Community Slack](https://img.shields.io/badge/Slack-%23gradleup-brightgreen?style=flat&logo=slack)](./#slack)
+
 ## GitHub Issues
 
 Each project has GitHub issues.

mkdocs.yml

@@ -172,7 +172,7 @@ extra:
       link: https://github.com/GradleUp
       name: GitHub
     - icon: fontawesome/brands/slack
-      link: docs/community/participate.md#slack
+      link: https://gradleup.com/docs/community/participate/#slack
       name: Slack
 #  analytics:
 #    provider: google