docs(ecr-assets): mention CDK_DOCKER environment variable in README

[ymotongpoo]

Issue # (if applicable)

Closes #32585.

Reason for this change

This change adds description that CDK_DOCKER environment variable is also effective in aws-ecr-assets module like aws-s3-assets.

Description of changes

Just a documentation change. No code change.

Describe any new or updated permissions being added

N/A

Description of how you validated changes

I confirmed the environment variable is effective locally.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[WinterYukky]

Nice!!

[kaizencc]

Thanks!

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 6ce62a7
• Result: SUCCEEDED
• Build Logs (available for 30 days)

Powered by github-codebuild-logs, available on the AWS Serverless Application Repository

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

This pull request has been removed from the queue for the following reason: pull request dequeued.

Pull request #32586 has been dequeued. The pull request could not be merged. This could be related to an activated branch protection or ruleset rule that prevents us from merging. (detail: 4 of 6 required status checks are expected.).

You should look at the reason for the failure and decide if the pull request needs to be fixed or if you want to requeue it.

If you want to requeue this pull request, you need to post a comment with the text: @mergifyio requeue

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[ymotongpoo]

@Mergifyio requeue

[mergify]

requeue

❌ Command disallowed due to command restrictions in the Mergify configuration.

• sender-permission >= write