feat: add docker labels

[AhnSeongHyun]

Issue #, if available:

Description of changes:

• Add docker-labels to optional action input(action.yml)
• Apply docker-labes to ecs task definition dockerLabels.
• Add test to empty case and update case.
• Update README

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[AhnSeongHyun]

what is problem??

[v3rm0n]

Since AWS Fargate does not copy image labels to the containers, this change would be welcome. Otherwise it's pretty hard to add a git commit sha as a label to the container.

[justin1291]

Are there any issues with this? It would be a really useful feature.

[amazreech]

Hi @AhnSeongHyun, thank you so much for your contribution. Apologies on the delay.
We will be working on reviewing this Pull Request. In the mean time please ensure that below steps, if not already done, are taken care of in your PR:

1. Verify if PR follows semantic pull request conventions.

2. Please be sure to run npm run package command to update dist/ folder with latest dependencies.

3. Resolve merge conflicts on the PR if any.

[amazreech]

This feature should be covered by PR 274.
Please feel free to re-open if the issue is not addressed.