chore: Add upgrade path info for terraform platform modules release v…

…ersion 6 (#312)

CHANGELOG.md

@@ -11,6 +11,28 @@
 
 * DBTP-1395 Add CloudFront and application load balancer origin verification secret for IP Filter spoofing ([#273](https://github.com/uktrade/terraform-platform-modules/issues/273)) ([7c182e0](https://github.com/uktrade/terraform-platform-modules/commit/7c182e002ffc2ad465dfef255c086af114e53e97))
 
+## Upgrade Path
+
+To upgrade to version 6 of terraform-platform-modules you can modify the 
+`<application>-deploy/platform-config.yml` for the environments that you want to upgrade (put the `versions` property in an individual environment or under the `*` to apply to all environments)
+
+```
+  environments:
+  "*":
+    accounts:
+      deploy:
+        name: "platform-sandbox"
+        id: "563763463626"
+      dns:
+        name: "dev"
+        id: "011755346992"
+    vpc: platform-sandbox-dev
+  dev:
+    versions:                        # add "versions" property
+      terraform-platform-modules: 6  # set "terraform-platform-modules" property to 6
+  ...
+```
+
 ## [5.15.0](https://github.com/uktrade/terraform-platform-modules/compare/5.14.0...5.15.0) (2025-01-07)