docs: add another commit about triggering a txn to userguide

Author: fubuloubu

docs/userguides/development.md

@@ -146,6 +146,7 @@ def update_table(log):
 @app.on_(chain.blocks)
 def use_table(blk):
     if app.state.table[...].mean() > app.state.table[...].sum():
+        # Trigger your app to send a transaction from `app.signer`
         contract.myMethod(..., sender=app.signer)
     ...
 ```