[docs] Add Docker setup for building documentation

[pmady]

Link the Issue(s) this Pull Request is related to.

• [docs] Create docker setup for building docs #1869
• [docs] Enhancement: Update and improve OpenCue documentation #1800

Summarize your change.

Add a comprehensive Docker-based setup for building OpenCue documentation without requiring a local Ruby installation. This provides multiple interfaces (helper script, Make, Docker Compose, and direct Docker) to accommodate different workflows and ensure consistent build environments across all platforms.

Changes:

• Add Dockerfile with Ruby 3.2 Alpine base image
• Add docker-compose.yml with build, serve, and ci profiles
• Add docker-build.sh helper script with fallback support
• Add Makefile for Make-based Docker commands
• Add .dockerignore for optimized builds
• Add DOCKER.md with comprehensive documentation
• Update README.md to recommend Docker setup as Option 1

Features:

• No Ruby installation required
• Live reload development server
• Persistent gem caching for faster builds
• CI/CD ready with clean build profile
• Backward compatible with local Ruby setup
• Supports Docker Compose v1, v2, or direct Docker commands

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: pmady / name: Pavan Madduri (35b81aa, e100216)

[lithorus]

Really nice setup.
Seems to work as intended, but perhaps you could also add it to CI/CD?

[pmady]

Included the docker set-up in github workflow
Before

- name: Setup Ruby
  uses: ruby/setup-ruby@v1
  with:
    ruby-version: '3.2'
    bundler-cache: true

- name: Build with Jekyll
  run: bundle exec jekyll build

After

- name: Set up Docker Buildx
uses: docker/setup-buildx-action@v3

- name: Build Docker image
run: docker build -t opencue-docs:ci .

- name: Build with Jekyll using Docker
run: docker run --rm -v "$(pwd):/docs" opencue-docs:ci bundle exec jekyll build

[ramonfigueiredo]

Thanks, @pmady

Great job!