This PR addresses the hardcoded dependency versions in the Dockerfile by implementing automatic fetching of the latest released versions of CMake and Catch2.

Changes Made

Dockerfile Updates

• Added ARG CMAKE_VERSION and ARG CATCH2_VERSION build arguments with current versions as defaults for backward compatibility
• Implemented shell parameter expansion to handle version string formatting (removing "v" prefix for filenames)
• Updated download URLs to use parameterized versions instead of hardcoded v4.0.3 (CMake) and v3.8.1 (Catch2)

GitHub Actions Workflow Enhancement

• Added steps to fetch latest release versions from GitHub API using curl and jq
• Modified Docker build process to pass fetched versions as build arguments
• Maintains existing scheduled build functionality while now using latest versions automatically

Documentation

• Updated README.md with examples for building with specific versions
• Documented the automatic version fetching behavior in GitHub Actions

Testing

• ✅ Verified variable substitution logic with different version formats
• ✅ Tested Docker build argument passing with custom versions
• ✅ Confirmed backward compatibility with default values
• ✅ Validated that the GitHub Actions workflow correctly passes build arguments

Benefits

• Automatic Updates: The daily scheduled build (cron: '34 16 * * *') will now automatically use the latest available versions
• Backward Compatibility: Manual builds continue to work with sensible defaults
• Flexibility: Developers can override versions for testing or specific requirements
• Maintenance Reduction: No more manual version updates required

Example usage:

# Uses defaults (current behavior maintained)
docker build -t cpp-runner .

# Uses specific versions
docker build --build-arg CMAKE_VERSION=v3.29.0 --build-arg CATCH2_VERSION=v3.7.1 -t cpp-runner .

Fixes #1.

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