✨ Add build digests to versions.json

[nikolaik]

Fixes #222

[Copilot]

Pull Request Overview

This PR adds build digest functionality to versions.json by modifying the workflow to capture Docker image digests during the build process and include them in the build metadata.

• Adds a new digest field to the BuildVersion dataclass
• Implements load_build_contexts function to read build metadata from JSON files
• Updates CI workflow to store build digests and pass them to the release process

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/docker_python_nodejs/versions.py	Adds digest field to BuildVersion and implements load_build_contexts function
src/docker_python_nodejs/cli.py	Updates release command to use build contexts from files instead of generating versions
tests/test_all.py	Adds test coverage for the new load_build_contexts function
.github/workflows/build.yaml	Modifies workflow to capture and store build digests in artifacts

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