docs: adds an example for the action templates

Signed-off-by: Vincent Biret <vincentbiret@hotmail.com>

Author: baywet

versions/1.2.0-dev.md

@@ -635,6 +635,102 @@ paths:
           description: OK
 ```
 
+##### Action Template Example
+
+###### Source Description
+
+```yaml
+openapi: 3.2.0
+info:
+  title: Example API
+  version: 1.0.0
+paths:
+  /items:
+    get:
+      responses:
+        200:
+          description: OK
+  /some-items:
+    delete:
+      responses:
+        200:
+          description: OK
+```
+
+###### Overlay
+
+```yaml
+overlay: 1.2.0
+info:
+  title: Use templates to insert error responses
+  version: 1.0.0
+components:
+  actionTemplates:
+    errorResponse:
+      target: "$.paths['%param.pathItem%'].%param.operation%.responses"
+      update:
+        404:
+          description: Not Found
+          application/json:
+            schema:
+              type: object
+              properties:
+                '%param.propertyName%':
+                  type: string
+      description: Adds an error response to the %param.pathItem% path item %param.operation% operation
+      parameters:
+      - name: pathItem
+      - name: operation
+        default: get
+      - name: propertyName
+        default: errorMessage
+actions:
+- $ref: '#/components/actionTemplates/errorResponse'
+  parameterValues:
+    pathItem: '/items'
+- $ref: '#/components/actionTemplates/errorResponse'
+  parameterValues:
+    pathItem: '/some-items'
+    operation: delete
+    propertyName: deleteErrorMessage
+```
+
+###### Result description
+
+```yaml
+openapi: 3.2.0
+info:
+  title: Example API
+  version: 1.0.0
+paths:
+  /items:
+    get:
+      responses:
+        200:
+          description: OK
+        404:
+          description: Not Found
+          application/json:
+            schema:
+              type: object
+                properties:
+                  errorMessage:
+                    type: string
+  /some-items:
+    delete:
+      responses:
+        200:
+          description: OK
+        404:
+          description: Not Found
+          application/json:
+            schema:
+              type: object
+                properties:
+                  deleteErrorMessage:
+                    type: string
+```
+
 ### Specification Extensions
 
 While the Overlay Specification tries to accommodate most use cases, additional data can be added to extend the specification at certain points.