add missing channels of sig-release subprojects

Signed-off-by: Nikolaos Moraitis <[email protected]>

Author: droslean

communication/slack-config/sig-release/config.yaml

@@ -1,7 +1,9 @@
 channels:
   - name: sig-release
+  - name: release-bug-triage  
   - name: release-ci-signal
   - name: release-comms
+  - name: release-docs
   - name: release-management
     id: CJH2GBF7Y
   - name: release-notes