Request to expand the tool to China regions

Thanks for providing the useful tool, I tried it in two regions, it works for me in us-west-2, but failed in cn-northwest-1 and the first problem seems incorrect URI, for example, the [docker push command in buildspec](https://github.com/aws-samples/sagemaker-studio-image-build-cli/blob/d02e9794b016e880513739224115f20238a20d62/sagemaker_studio_image_build/data/buildspec.template.yml#L22) uses a hardcoded URI suffix `amazonaws.com`, but in China regions the suffix should be `amazonaws.com.cn`.

Would you fix the problems and enable the tool in China regions?

Start with sagemaker_studio_image_build/data/buildspec.template.yml at the linked Docker push command, then trace how the tool determines its AWS region and registry URI. The work is done when builds in cn-northwest-1 and other China regions use the correct regional URI suffix and the tool works there without breaking us-west-2.

Written by the indexing model from the issue text.