fix: example in readme

Author: Ho3einWave

README.md

@@ -16,7 +16,7 @@ npm install @mytonswap/sdk
 Here's a basic example of how to use the MyTonSwap SDK:
 
 ```ts
-import { MyTonSwapClient } from '@mytonswap/sdk';
+import { MyTonSwapClient, toNano } from '@mytonswap/sdk';
 
 const client = new MyTonSwapClient();
 
@@ -49,4 +49,4 @@ This project is licensed under the MIT License - see the [LICENSE](LICENSE) file
 
 ## Support
 
-If you have any questions or need help, feel free to open an issue on our [GitHub repository](https://github.com/MyTonSwap/sdk/issues).
+If you have any questions or need help, feel free to open an issue on our [GitHub repository](https://github.com/MyTonSwap/sdk/issues).