docs: adds a copy example for the overlay

overlay/example-copy-schema.md

@@ -0,0 +1,26 @@
+---
+layout: default
+parent: Overlays
+nav_order: 2
+title: 'Example: copy a schema'
+has_toc: false
+---
+
+# Example: copy a schema
+
+Ever needed to copy a schema so you don't need to maintain a copy which could become stale in your overlay document? This example copies the Foo component schema as a new Bar component schema.
+
+```yaml
+overlay: 1.0.0
+info:
+  title: Copy a schema component
+  version: 1.1.0
+actions:
+  - target: '$.components.schemas'
+    description: Ensure the target schema is present
+    update:
+      Bar: {}
+  - target: '$.components.schemas['Bar']'
+    copy: '$.components.schemas['Foo']'
+    description: Copy the Foo Schema to Bar
+```