Add Docker support and GitHub Container Registry CI workflow (#3)

* Add comprehensive Docker support with multi-stage builds
* Set up GitHub Container Registry integration
* Enhance CI/CD workflows with Docker build and push capabilities
* Add --help and --version flags to main application
* Update documentation with Docker usage examples
* Implement security best practices for container deployment

README.md

@@ -10,6 +10,9 @@ A Go-based parser that converts Articulate Rise e-learning content to various fo
 [![Last commit](https://img.shields.io/github/last-commit/kjanat/articulate-parser?label=Last%20commit)][Commits]
 [![GitHub Issues or Pull Requests](https://img.shields.io/github/issues/kjanat/articulate-parser?label=Issues)][Issues]
 [![CI](https://img.shields.io/github/actions/workflow/status/kjanat/articulate-parser/ci.yml?logo=github&label=CI)][Build]
+[![Docker](https://img.shields.io/github/actions/workflow/status/kjanat/articulate-parser/docker.yml?logo=docker&label=Docker)][Docker workflow]
+[![Docker Image](https://img.shields.io/badge/docker-ghcr.io-blue?logo=docker&logoColor=white)][Docker image]
+[![Docker Size](https://img.shields.io/docker/image-size/kjanat/articulate-parser?logo=docker&label=Image%20Size)][Docker image]
 [![Codecov](https://img.shields.io/codecov/c/gh/kjanat/articulate-parser?token=eHhaHY8nut&logo=codecov&logoColor=%23F01F7A&label=Codecov)][Codecov]
 
 ## System Architecture
@@ -101,7 +104,7 @@ The system follows **Clean Architecture** principles with clear separation of co
 
 ### Prerequisites
 
--   Go, I don't know the version, but I use go1.24.2 right now, and it works, see the [CI][Build] workflow where it is tested.
+-   Go, I don't know the version, but I have [![Go version](https://img.shields.io/github/go-mod/go-version/kjanat/articulate-parser?label=)][gomod] configured right now, and it works, see the [CI][Build] workflow where it is tested.
 
 ### Install from source
 
@@ -200,6 +203,130 @@ Then run:
 ./articulate-parser input.json md output.md
 ```
 
+## Docker
+
+The application is available as a Docker image from GitHub Container Registry.
+
+### 🐳 Docker Image Information
+
+- **Registry**: `ghcr.io/kjanat/articulate-parser`
+- **Platforms**: linux/amd64, linux/arm64
+- **Base Image**: Scratch (minimal footprint)
+- **Size**: ~15-20MB compressed
+
+### Quick Start
+
+```bash
+# Pull the latest image
+docker pull ghcr.io/kjanat/articulate-parser:latest
+
+# Show help
+docker run --rm ghcr.io/kjanat/articulate-parser:latest --help
+```
+
+### Available Tags
+
+| Tag | Description | Use Case |
+|-----|-------------|----------|
+| `latest` | Latest stable release from master branch | Production use |
+| `edge` | Latest development build from master branch | Testing new features |
+| `v1.x.x` | Specific version releases | Production pinning |
+| `develop` | Development branch builds | Development/testing |
+| `feature/docker-ghcr` | Feature branch builds | Feature testing |
+| `master` | Latest master branch build | Continuous integration |
+
+### Usage Examples
+
+#### Process a local file
+
+```bash
+# Mount current directory and process a local JSON file
+docker run --rm -v $(pwd):/workspace \
+  ghcr.io/kjanat/articulate-parser:latest \
+  /workspace/input.json markdown /workspace/output.md
+```
+
+#### Process from URL
+
+```bash
+# Mount output directory and process from Articulate Rise URL
+docker run --rm -v $(pwd):/workspace \
+  ghcr.io/kjanat/articulate-parser:latest \
+  "https://rise.articulate.com/share/xyz" docx /workspace/output.docx
+```
+
+#### Export to different formats
+
+```bash
+# Export to HTML
+docker run --rm -v $(pwd):/workspace \
+  ghcr.io/kjanat/articulate-parser:latest \
+  /workspace/course.json html /workspace/course.html
+
+# Export to Word Document
+docker run --rm -v $(pwd):/workspace \
+  ghcr.io/kjanat/articulate-parser:latest \
+  /workspace/course.json docx /workspace/course.docx
+
+# Export to Markdown
+docker run --rm -v $(pwd):/workspace \
+  ghcr.io/kjanat/articulate-parser:latest \
+  /workspace/course.json md /workspace/course.md
+```
+
+#### Batch Processing
+
+```bash
+# Process multiple files in a directory
+docker run --rm -v $(pwd):/workspace \
+  ghcr.io/kjanat/articulate-parser:latest \
+  bash -c "for file in /workspace/*.json; do
+    /articulate-parser \"\$file\" md \"\${file%.json}.md\"
+  done"
+```
+
+### Docker Compose
+
+For local development, you can use the provided `docker-compose.yml`:
+
+```bash
+# Build and run with default help command
+docker-compose up articulate-parser
+
+# Process files using mounted volumes
+docker-compose up parser-with-files
+```
+
+### Building Locally
+
+```bash
+# Build the Docker image locally
+docker build -t articulate-parser:local .
+
+# Run the local image
+docker run --rm articulate-parser:local --help
+
+# Build with specific version
+docker build --build-arg VERSION=local --build-arg BUILD_TIME=$(date -u +%Y-%m-%dT%H:%M:%SZ) -t articulate-parser:local .
+```
+
+### Environment Variables
+
+The Docker image supports the following build-time arguments:
+
+| Argument | Description | Default |
+|----------|-------------|---------|
+| `VERSION` | Version string embedded in the binary | `dev` |
+| `BUILD_TIME` | Build timestamp | Current time |
+| `GIT_COMMIT` | Git commit hash | Current commit |
+
+### Docker Security
+
+- **Non-root execution**: The application runs as a non-privileged user
+- **Minimal attack surface**: Built from scratch base image
+- **No shell access**: Only the application binary is available
+- **Read-only filesystem**: Container filesystem is read-only except for mounted volumes
+
 ## Development
 
 ### Code Quality
@@ -329,6 +456,8 @@ This is a utility tool for educational content conversion. Please ensure you hav
 [Build]: https://github.com/kjanat/articulate-parser/actions/workflows/ci.yml
 [Codecov]: https://codecov.io/gh/kjanat/articulate-parser
 [Commits]: https://github.com/kjanat/articulate-parser/commits/master/
+[Docker workflow]: https://github.com/kjanat/articulate-parser/actions/workflows/docker.yml
+[Docker image]: https://github.com/kjanat/articulate-parser/pkgs/container/articulate-parser
 [Go report]: https://goreportcard.com/report/github.com/kjanat/articulate-parser
 [gomod]: go.mod
 [Issues]: https://github.com/kjanat/articulate-parser/issues