update ecr gallery

Signed-off-by: sirutBuasai <sirutbuasai27@outlook.com>

Author: sirutBuasai

docs/reference/available_images.template.md

@@ -4,10 +4,14 @@ This page is for referencing our supported deep learning containers.
 
 Refer to the tables below for all images that are available in AWS ECR repositories.
 
+## ECR Public Gallery
+
 Additionally, we also publish the following images to [ECR Public Gallery](https://gallery.ecr.aws/deep-learning-containers).
 
 {{ public_ecr_image_list }}
 
+---
+
 ## Region Availability
 
 | Region                    | Code           | General | Neuron | Example URL                                                                          |