fix: add tx filterer setup (#441)

fixes the setup for gateway

Author: sarahschwartz

content/10.zk-stack/20.running/25.gateway-settlement-layer.md

@@ -73,6 +73,12 @@ This guide assumes you already have `zkstackup` and the required system dependen
       --chain gateway --update-submodules false
     ```
 
+1. Setup the transaction filterer for `gateway`:
+
+    ```bash
+    zkstack chain gateway create-tx-filterer --chain gateway --ignore-prerequisites
+    ```
+
 1. Transform `gateway` chain from rollup into a ZKsync Gateway settlement layer:
 
     ```bash