Add cadence url to migration guide (#506)

Co-authored-by: Chase Fleming <[email protected]>

docs/build/cadence-migration-guide.md

@@ -11,5 +11,6 @@ Coming this year, the network will be upgrading to the Cadence 1.0. This means t
 We have created several resources to help developers update their applications. Use the following links to start upgrading your contracts and to understand how the network upgrade will affect your application:
 
 - [Understand the upgrade, the timeline, and how it affects you](https://forum.flow.com/t/cadence-1-0-upgrade-plan/5477)
+- [Learn how Cadence will be changing for 1.0](https://forum.flow.com/t/update-on-cadence-1-0/5197)
 - [Learn how to update your Flow CLI to test against Cadence 1.0](https://forum.flow.com/t/update-on-cadence-1-0/5197/7)
 - [Check out the Cadence language 1.0 docs](https://cadencelang.dev/docs/1.0/)