chore: add v8 migration doc

docs/migrations/v7-to-v8.md

@@ -0,0 +1,29 @@
+# Migrating from v7 to v8
+
+This guide provides instructions for migrating to version `v8.0.0` of ibc-go.
+
+There are four sections based on the four potential user groups of this document:
+
+- [Migrating from v7 to v8](#migrating-from-v7-to-v8)
+  - [Chains](#chains)
+  - [IBC Apps](#ibc-apps)
+  - [Relayers](#relayers)
+  - [IBC Light Clients](#ibc-light-clients)
+
+**Note:** ibc-go supports golang semantic versioning and therefore all imports must be updated on major version releases.
+
+## Chains
+
+- No relevant changes were made in this release.
+
+## IBC Apps
+
+TODO: https://github.com/cosmos/ibc-go/pull/3303
+
+## Relayers
+
+- No relevant changes were made in this release.
+
+## IBC Light Clients
+
+- No relevant changes were made in this release.