Enable the @rustbot ready/author/blocked shortcuts

Given that they can set pretty much all the other flags (including e.g.
nominating an issue) these are part of the regular issue/ACP workflow
and thus seem sensible to add.

Author: tomassedovic

triagebot.toml

@@ -20,6 +20,10 @@ allow-unauthenticated = [
     "initial-comment-period",
 ]
 
+
+# Enable rustbot ready/author/blocked shortcuts
+[shortcut]
+
 # [major-change]
 # second_label = "initial-comment-period"
 # meeting_label = "I-nominated"