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

Dockerfile.dev

@@ -0,0 +1,78 @@
+# Development Dockerfile with shell access
+# Uses Alpine instead of scratch for debugging
+
+# Build stage - same as production
+FROM golang:1.23-alpine AS builder
+
+# Install git and ca-certificates (needed for fetching dependencies and HTTPS)
+RUN apk add --no-cache git ca-certificates tzdata file
+
+# Create a non-root user
+RUN adduser -D -u 1000 appuser
+
+# Set the working directory
+WORKDIR /app
+
+# Copy go mod files
+COPY go.mod go.sum ./
+
+# Download dependencies
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Build the application
+# Disable CGO for a fully static binary
+# Use linker flags to reduce binary size and embed version info
+ARG VERSION=dev
+ARG BUILD_TIME
+ARG GIT_COMMIT
+# Docker buildx automatically provides these for multi-platform builds
+ARG BUILDPLATFORM
+ARG TARGETPLATFORM  
+ARG TARGETOS
+ARG TARGETARCH
+ARG TARGETVARIANT
+
+# Debug: Show build information
+RUN echo "Building for platform: $TARGETPLATFORM (OS: $TARGETOS, Arch: $TARGETARCH, Variant: $TARGETVARIANT)" \
+&& echo "Build platform: $BUILDPLATFORM" \
+&& echo "Go version: $(go version)"
+
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build \
+-ldflags="-s -w -X github.com/kjanat/articulate-parser/internal/version.Version=${VERSION} -X github.com/kjanat/articulate-parser/internal/version.BuildTime=${BUILD_TIME} -X github.com/kjanat/articulate-parser/internal/version.GitCommit=${GIT_COMMIT}" \
+-o articulate-parser \
+./main.go
+
+# Verify the binary architecture
+RUN file /app/articulate-parser || echo "file command not available"
+
+# Development stage - uses Alpine for shell access
+FROM alpine:3.21.3
+
+# Install minimal dependencies
+RUN apk add --no-cache ca-certificates tzdata
+
+# Copy the binary
+COPY --from=builder /app/articulate-parser /articulate-parser
+
+# Copy the non-root user configuration
+COPY --from=builder /etc/passwd /etc/passwd
+
+# Switch to non-root user
+USER appuser
+
+# Set the binary as entrypoint
+ENTRYPOINT ["/articulate-parser"]
+
+# Default command shows help
+CMD ["--help"]
+
+# Add labels for metadata
+LABEL org.opencontainers.image.title="Articulate Parser (Dev)"
+LABEL org.opencontainers.image.description="Development version of Articulate Parser with shell access"
+LABEL org.opencontainers.image.vendor="kjanat"
+LABEL org.opencontainers.image.licenses="MIT"
+LABEL org.opencontainers.image.source="https://github.com/kjanat/articulate-parser"
+LABEL org.opencontainers.image.documentation="https://github.com/kjanat/articulate-parser/blob/master/DOCKER.md"