feat: ghcr publish workflow

[ShubyM]

Github action to publish kubectl-ai image to GHCR, part of #264.

Testing locally using act

1. In the docker/build-push-action step, set push: false
2. (Optional) Add load: true in the same step to load the built image into your local Docker daemon for inspection
3. Run the following command

act -j build-and-publish

[droot]

@ShubyM can you update the description with the details on how you tested it locally ?

[Copilot]

Pull Request Overview

This PR introduces a GitHub Actions workflow to build and publish the kubectl-ai Docker image to GitHub Container Registry (GHCR), addressing issue #264. The workflow enables automated container image publishing for the project.

Key changes:

• Adds a new GitHub Actions workflow for Docker image publishing
• Configures GHCR as the target registry with proper authentication
• Sets up automated tagging with latest and timestamp-based tags

Comments suppressed due to low confidence (1)

.github/workflows/publish-image.yaml:15

• [nitpick] The job name 'build-and-push' is inconsistent with the actual job name 'build-and-publish' used in the PR description and testing instructions. Consider renaming to 'build-and-publish' for consistency.

  build-and-push:

[Copilot]

The workflow is triggered by 'workflow_dispatch' (manual trigger) but includes a 'type=schedule' tag pattern. This tag type is only relevant for scheduled workflows and will not be applied for manual triggers. Consider using 'type=ref,event=workflow_dispatch' or removing this tag type.

Suggested change

type=schedule,pattern={{date 'YYYYMMDD-HHmm' tz='UTC'}}