Add fleetlock docs and links to addons

* Add links to fleetlock for Fedora CoreOS reboot coordination
* https://github.com/poseidon/fleetlock

docs/addons/fleetlock.md

@@ -0,0 +1,39 @@
+## fleetlock
+
+[fleetlock](https://github.com/poseidon/fleetlock) is a reboot coordinator for Fedora CoreOS nodes. It implements the [FleetLock](https://github.com/coreos/airlock/pull/1/files) protocol for use as a [Zincati](https://github.com/coreos/zincati) lock [strategy](https://github.com/coreos/zincati/blob/master/docs/usage/updates-strategy.md) backend.
+
+Declare a Zincati `fleet_lock` strategy when provisioning Fedora CoreOS nodes via [snippets](/advanced/customization/#hosts).
+
+```yaml
+variant: fcos
+version: 1.0.0
+storage:
+  files:
+    - path: /etc/zincati/config.d/55-update-strategy.toml
+      contents:
+        inline: |
+          [updates]
+          strategy = "fleet_lock"
+          [updates.fleet_lock]
+          base_url = "http://10.3.0.15/"
+```
+
+```tf
+module "nemo" {
+  ...
+  controller_snippets = [
+    file("./snippets/zincati-strategy.yaml"),
+  ]
+  worker_snippets = [
+    file("./snippets/zincati-strategy.yaml"),
+  ]
+}
+```
+
+Apply fleetlock based on the example manifests.
+
+```sh
+git clone git@github.com:poseidon/fleetlock.git
+kubectl apply -f examples/k8s
+```
+

docs/addons/overview.md

@@ -1,8 +1,9 @@
 # Addons
 
-Every Typhoon cluster is verified to work well with several post-install addons.
+Typhoon clusters are verified to work well with several post-install addons.
 
 * Nginx [Ingress Controller](ingress.md)
 * [Prometheus](prometheus.md)
 * [Grafana](grafana.md)
+* [fleetlock](fleetlock.md)