Reference the Slack archive

Author: oleg-nenashev

docs/community/participate.md

@@ -4,16 +4,26 @@
 
 ## GitHub Issues
 
-Each project has GitHub issues.
+Each project repository has GitHub Issues enabled.
 Please raise bugs and discuss feature requests there.
 
 ## Slack
 
 We have a `#gradleup` public channel on the
 [Gradle Community Slack](https://community.gradle.org/contributing/community-slack/).
-For now, this chat is used for all development and end user discussions.
-In the future, we may introduce more channels.
+This chat is used for real-time development and end user discussions.
+For longer-term discussions, e.g. architecture proposals or feature requests,
+it is highly recommended to use GitHub Issues in the respective repositories.
 
 The following components have custom channels:
 
 - `#dev-shadow-plugin` - development of the Shadow Plugin.
+
+In the future, we may introduce more channels.
+
+## Slack Archive
+
+Gradle Community Slack uses the free plan,
+so the history of `#gradleup` is limited to 3 months.
+You can find the communications archive for previous dates
+[here](https://www.linen.dev/s/gradle-community/c/gradleup).