Add blurb about Privy and point folks to Privy docs (#1122)

Author: dgca

docs/base-chain/builder-codes/app-developers.mdx

@@ -126,6 +126,12 @@ When you register on [base.dev](https://base.dev/), you will receive a **Builder
   </Step>
 </Steps>
 
+## Using Privy
+
+Privy provides a `dataSuffix` plugin that automatically appends your Builder Code to all transactions—including both EOA transactions and ERC-4337 smart wallet user operations.
+
+See the [Privy Builder Codes integration guide](https://docs.privy.io/recipes/evm/base-builder-codes) for setup instructions.
+
 ## Legacy: Per-Transaction Approach
 
 <Accordion title="Appending dataSuffix Per-Transaction">