docs(addons): update documentation

docs/addons.md

@@ -89,7 +89,42 @@ Read more about cluster autoscaler in the [official documentation](https://githu
 ##### Expander strategies
 Cluster autoscaler supports several different [expander strategies](https://github.com/kubernetes/autoscaler/blob/master/cluster-autoscaler/FAQ.md#what-are-expanders).
 
-Note that the `priority` expander requires additional configuration through a ConfigMap as described in [its documentation](https://github.com/kubernetes/autoscaler/blob/master/cluster-autoscaler/expander/priority/readme.md) - you will need to create this ConfigMap in your cluster before selecting this expander.
+###### Priority Expander configuration
+{{ kops_feature_table(kops_added_default='1.26') }}
+
+The `priority` expander requires additional configuration through a ConfigMap as described in [its documentation](https://github.com/kubernetes/autoscaler/blob/master/cluster-autoscaler/expander/priority/readme.md)
+
+When `expander: priority` is defined kOps will create this ConfigMap based on the InstanceGroup spec. You can change priority of each instance group by adding the followig to the InstanceGroup spec.
+
+```yaml
+spec:
+  autoscale: true
+  autoscalePriority: 100
+```
+
+If `autoscalePriority` is not set, it will default to 0.
+
+If you need a more complex configuration, eg use regex for matching the InstanceGoup, you can provide your own custom configuration. If this is configured, the priority set on the InstanceGroup specs are ignored.
+
+```yaml
+clusterAutoscaler:
+  customPriorityExpanderConfig:
+    100:
+    - .*foo.*
+    50:
+    - .*bar.*
+    0:
+    - .*
+```
+
+###### Disable
+
+If you want to manage the priority expander ConfigMap outside of kOps, you can disable the ConfigMap creation by adding the following to the Cluster spec:
+
+```yaml
+clusterAutoscaler:
+  createPriorityExpanderConfig: false
+```
 
 ##### Disabling cluster autoscaler for a given instance group
 {{ kops_feature_table(kops_added_default='1.20') }}