chore: add migration guide to 0.33 (#997)

Author: vasco-santos

doc/migrations/v0.32-v0.33.md

@@ -0,0 +1,14 @@
+<!--Specify versions for migration below-->
+# Migrating to libp2p@33
+
+A migration guide for refactoring your application code from libp2p v0.32.x to v0.33.0.
+
+## Table of Contents
+
+- [Module Updates](#module-updates)
+
+## Module Updates
+
+Libp2p uses a datastore implementation for Peerstore persistence and for the DHT state. While libp2p defaults to a datastore implementation, it can receive any implementation of a datastore compliant with the [interface-datastore](https://github.com/ipfs/js-ipfs-interfaces/tree/master/packages/interface-datastore) via its configuration.
+
+In this release, we updated to `interface-datastore@6.0.0`. As a result, libp2p users relying on a configured datastore should update it to a compliant implementation for updating libp2p.