Add SDK migration guide

docs/developer-guides/sdk-update-v1.3.0-to-v1.3.1.md

@@ -0,0 +1,35 @@
+# Migration from v1.3.0 to v1.3.1
+
+This guide present steps required to migrate you project from Partner Chains SDK v1.3.0 to v1.3.1.
+
+## Update SDK dependency
+
+In your cargo.toml files, update the `partner-chains` dependency from `v1.3.0` to `v1.3.1`.
+
+## Update Runtime
+
+In your Runtime crate find where instance of `RuntimeVersion` is created and increase the `spec_version`,
+because runtime code update is required.
+
+In your Rutime find `impl pallet_sidechain::Config` for your runtime,
+and add following code to it:
+```rust
+type MainChainScripts = sp_session_validator_management::MainChainScripts;
+
+fn set_main_chain_scripts(scripts: Self::MainChainScripts) {
+	pallet_session_validator_management::MainChainScriptsConfiguration::<Runtime>::set(scripts);
+}
+```
+
+If you have any Runtime test, is will be necessary to update mock as well:
+```rust
+type MainChainScripts = ();
+
+fn set_main_chain_scripts(scripts: Self::MainChainScripts) {}
+```
+
+## Update the on-chain runtime code
+
+Perform regular runtime code update procedure:
+* update nodes to version build with Partner Chains SDK v1.3.1
+* use `system/setCode` extrinsic to update runtime code build with Partner Chains SDK v1.3.1