added info for unity embedded wallet boilerplates

Author: andygruening

sdk/unity/bootstrap.mdx

@@ -81,6 +81,11 @@ BoilerplateFactory.OpenEcosystemWalletTransactions(parent, wallet);
 
 ## Embedded Wallet
 
+<Info>
+    Embedded Wallet Boilerplates use Arbitrum Sepolia by default. Do the following to switch them to your preferred
+    chain `EmbeddedWalletAdapter.GetInstance().Chain = Chain.TestnetPolygonAmoy;`
+</Info>
+
 ### Login Window
 
 Create the `EmbeddedWalletLoginWindow` prefab to authenticate users as a Guest, with Email OTP, Google- or Apple Sign In.