chore: add migration guide template (#711)

MIGRATION_TEMPLATE.md

@@ -0,0 +1,45 @@
+<!--Specify versions for migration below-->
+# Migrating to libp2p@__
+
+A migration guide for refactoring your application code from libp2p v__ to v__.
+
+## Table of Contents
+
+- [API](#api)
+- [Module Updates](#module-updates)
+
+## API
+
+<!--Describe breaking APIs with examples for Before and After
+Example:
+
+### Peer Discovery
+
+__Describe__
+
+**Before**
+
+```js
+
+```
+
+**After**
+
+```js
+
+```
+
+-->
+
+## Module Updates
+
+With this release you should update the following libp2p modules if you are relying on them:
+
+<!--Specify module versions in JSON for migration below.
+It's recommended to check package.json changes for this: 
+`git diff <release> <prev> -- package.json`
+-->
+
+```json
+
+```