Adds missing annotation field from swagger.yml

Signed-off-by: Edward Wilde <ewilde@gmail.com>

api-docs/swagger.yml

@@ -440,6 +440,10 @@ definitions:
         type: object
         additionalProperties:
           type: string
+      annotations:
+        type: object
+        additionalProperties:
+          type: string
     required:
     - name
     - image
@@ -450,4 +454,4 @@ definitions:
     - labels
 externalDocs:
   description: More documentation available on Github
-  url: 'https://github.com/openfaas/faas'
+  url: 'https://github.com/openfaas/faas'