Added NTT to README

Author: kev1n-peters

README.md

@@ -131,6 +131,21 @@ See the "Arbitrary Token" example in [the config docs](https://docs.wormhole.com
 
 Please note you have to [register a token](https://portalbridge.com/advanced-tools/#/register) with the token bridge before you can use it in Connect.
 
+### Configuring Custom NTT (Native Token Transfer) Groups
+To configure custom NTT groups, include an `nttGroups` key in your configuration.
+
+```ts
+const config: WormholeConnectConfig = {
+  nttGroups: {
+    // Your custom NTT groups go here
+  }
+}
+```
+
+For a practical example of how to structure your custom NTT groups, refer to the [nttGroups.ts](https://github.com/wormhole-foundation/wormhole-connect/blob/development/wormhole-connect/src/config/testnet/nttGroups.ts) file.
+
+Please note that the `tokenKey` specified in your custom NTT group must correspond to an existing entry in the tokensConfig, whether it's a built-in or a custom token.
+
 ### Custom Theme
 
 You can also customize Connect's color scheme by providing a `WormholeConnectTheme` as the `theme` prop.