Update github-token-available-permissions.md

Author: smashwilson

data/reusables/github-actions/github-token-available-permissions.md

@@ -6,6 +6,7 @@ permissions:
   checks: read|write|none
   contents: read|write|none
   deployments: read|write|none
+  discussions: read|write|none
   issues: read|write|none
   packages: read|write|none
   pull-requests: read|write|none