chore(docs): update readme (#42)

Author: goodroot

README.md

@@ -126,6 +126,6 @@ Note that the migrated code uses the HTTP sender instead of the TCP one.
 ## Community
 
 If you need help, have additional questions or want to provide feedback, you
-may find us on [Slack](https://slack.questdb.io).
-You can also [sign up to our mailing list](https://questdb.io/community/)
+may find in our [Community Forum](https://community.questdb.io/).
+You can also [sign up to our mailing list](https://questdb.io/contributors/)
 to get notified of new releases.