Adding a note about USDC and USDT for AppKit Pay

Author: rohit-710

appkit/payments/pay-with-exchange.mdx

@@ -50,6 +50,10 @@ Currently, AppKit Pay with Exchange and Self-Custodial Wallets supports the foll
 - USDT -> Ethereum, Optimism, Arbitrum, Polygon, Solana
 - Native Solana
 
+<Note>
+  Currently, USDC and USDT on Solana is only available via Pay with Exchange. It will soon be available via Pay with Self-Custodial Wallets.
+</Note>
+
 **Both EVM and Solana networks and their assets can be added, subject to exchange compatibility.**
 
 For access to additional networks or assets, please contact sales@reown.com.