Add Docker support for easier setup

[Ketbome]

This PR adds Docker and Docker Compose support to make it easier to run import-gitlab-commits without needing to install Go locally.

Not everyone has Go installed, and some users might prefer using Docker for:

• Consistent environment across different systems
• Easier setup (just Docker + credentials)
• No need to manage Go versions or dependencies
• Isolation from the host system

[Copilot]

Pull Request Overview

This PR adds Docker support to the import-gitlab-commits tool, enabling users to run the application in a containerized environment alongside the existing native Go build option.

• Introduces Docker and Docker Compose configurations for containerized execution
• Adds comprehensive documentation for Docker usage in README
• Integrates Docker build validation into the CI/CD pipeline

Reviewed Changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Dockerfile	Multi-stage build configuration using Go 1.24 and Alpine Linux for a minimal runtime image
docker-compose.yml	Service definition with environment variable handling and volume mounting for output
.dockerignore	Excludes unnecessary files from Docker build context (tests, docs, IDE configs)
.env.example	Template file with documentation for required environment variables
README.md	Comprehensive Docker usage documentation including Docker Compose and standalone Docker options
Makefile	New docker-build and docker-run targets for local development
.github/workflows/build.yml	Adds Docker build validation to CI pipeline
.gitignore	Excludes generated output directory
output/.gitkeep	Placeholder to ensure output directory exists in repository

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[alexandear]

Thank you!