feat: add v1.26.3 upgrade doc

Author: omissis

docs/upgrades/v1.26.2-to-v1.26.3.md

@@ -0,0 +1,32 @@
+# Kubernetes Fury Distribution v1.26.2 to 1.26.3 Upgrade Guide
+
+This guide describes the steps to follow to upgrade the Kubernetes Fury Distribution (KFD) from v1.26.2 to 1.26.3.
+
+If you are running a custom set of modules, or different versions than the ones included with each release of KFD, please refer to each module's release notes.
+
+Notice that the guide will not cover changes related to the cloud provider, ingresses or pod placement changes. Only changes related to KFD and its modules.
+
+> ⛔️ **IMPORTANT**
+> we strongly recommend reading the whole guide before starting the upgrade process to identify possible blockers.
+
+## Upgrade procedure
+
+### 1. Using furyctl
+
+Change `.spec.distributionVersion` on your `furyctl.yaml` file with the new `v1.26.3`.
+
+Validate the schema using the new `v0.26.3` `furyctl` version:
+
+```bash
+furyctl validate config
+```
+
+Apply the new configuration on the cluster with:
+
+```bash
+furyctl create cluster
+```
+
+### 2. Using KFD directly
+
+There are no changes on the modules since the version v1.26.2.