schema: Move info about $defs into README

Turns out $comment is not allowed there according to another schema
meta-validator.

Author: Zash

config/schemas/README.md

@@ -85,6 +85,18 @@ EOF
 
 The output can be tweaked and inserted into `config/schemas/config.yaml` under `.properties`.
 
+To limit duplication, common properties that are used in many places can be placed under `.$defs` and referenced via `$ref: '#/$defs/thing'`
+
+```yaml
+$defs:
+  common:
+    title: Some Common Thing
+service:
+  title: The Service
+  common:
+    $ref: '#/$defs/common'
+```
+
 ## VSCode
 
 The plugin `redhat.vscode-yaml` can provide auto completion, validation and help texts from the schema.

config/schemas/config.yaml

@@ -7,13 +7,6 @@ description: |
   cluster and the workload cluster, but keep in mind that each configuration
   file will contain different settings.
 $defs:
-  $comment: |
-    Location for common types of things for reuse with a reference like
-
-    ```yaml
-    thing:
-      $ref: "#/$defs/thing"
-    ```
   kubernetesAffinity:
     $comment: Real k8s resources might have existing schemas that could be reused as-is
     properties: