[Feature Request] Package CLI as a Docker Image

### Description

Description
According to the README.md the only way to use the CLI is by installing via npm.

This request is to also package the CLI into a docker image so it can be used without the node dependency

### Acceptance Criteria

Docker image available such as public.ecr.aws/agentcore-cli/agentcore-cli:latest similar to how AWS CLI is available - https://docs.aws.amazon.com/cli/latest/userguide/getting-started-docker.html#cliv2-docker-install

### Additional Context

n/a

Start with README.md to understand the current npm-based CLI installation and usage, then review the linked AWS CLI Docker guidance for the expected user experience. Package the CLI as a Docker image and make an image available at a public registry location such as public.ecr.aws/agentcore-cli/agentcore-cli:latest; done means users can use it without installing Node.js.

Written by the indexing model from the issue text.