permit asyncawait-ondeck to be added by anyone

Still debating if this is the right approach
diff --git a/triagebot.toml b/triagebot.toml
index f350989..53c0e52 100644
--- a/triagebot.toml
+++ b/triagebot.toml
@@ -4,6 +4,7 @@
     "requires-nightly",
     # I-* without I-nominated
     "I-compilemem", "I-compiletime", "I-crash", "I-hang", "I-ICE", "I-slow",
+    "AsyncAwait-OnDeck",
 ]
 
 [assign]