readme-update (#1208)

Author: mahmud-bn

README.md

@@ -1,4 +1,5 @@
 # Web3-Onboard
+
 **easy way to connect users to dapps**
 
 ## Features
@@ -68,6 +69,10 @@ if (wallets[0]) {
 }
 ```
 
+**Onboard v1 migration guide**
+
+If you're coming from v1, we've created a [migration guide for you](https://docs.blocknative.com/onboard/migration-guide).
+
 ## Documentation
 
 For full documentation, check out the README.md for each package: