feat: support metadata config in docker config file

[m-artin-t]

Summary

Adds support for reading metadata-tags and metadata-flavor from the docker config file, with config values overriding action inputs.

Changes

• Created shared script shared/read-docker-config.sh to centralize config file reading
• Updated build action to use shared script and resolve metadata from config
• Added config file support to manifest action (with same default .docker-config.json)
• Config values override action inputs when present
• Updated documentation with examples

Config File Example

{
  "imageName": "your-org/your-image",
  "dockerfile": "./Dockerfile",
  "target": "production",
  "metadata-tags": "type=semver,pattern={{version}}\ntype=semver,pattern={{major}}.{{minor}}",
  "metadata-flavor": "latest=false"
}

This allows centralizing Docker metadata configuration in the config file rather than duplicating it across workflows.

🤖 Generated with Claude Code

[github-actions]

Release notes preview

Below is a preview of the release notes if your PR gets merged.

---

1.4.0 (2026-01-28)

Features

• support metadata config in docker config file (41cc49b)

Miscellaneous

• deps: update actions/checkout action to v6 (5d9f39e)
• deps: update dependency open-turo/renovate-config to v1.17.0 (271993d)
• deps: update pre-commit hook alessandrojcm/commitlint-pre-commit-hook to v9.24.0 (9e62a49)
• deps: update pre-commit hook rhysd/actionlint to v1.7.10 (f020128)

[tagoro9]

I know it's still in draft, but it would be helpful to understand the changes if you could add a bit of context in the description as to why this is needed vs enforcing standard tags via semantic release as we are doing today