Document message parameter to /images/create

This parameter was introduced 4 years ago in b857dadb33
as part of https://github.com/moby/moby/pull/15711, but has never made it to the API docs.

Signed-off-by: Jan Chren (rindeal) <dev.rindeal@gmail.com>

api/swagger.yaml

@@ -6667,6 +6667,10 @@ paths:
           in: "query"
           description: "Tag or digest. If empty when pulling an image, this causes all tags for the given image to be pulled."
           type: "string"
+        - name: "message"
+          in: "query"
+          description: "Set commit message for imported image."
+          type: "string"
         - name: "inputImage"
           in: "body"
           description: "Image content if the value `-` has been specified in fromSrc query parameter"