feat: add Paragon build-tokens command using tutor custom jobs

[Ang-m4]

Description

This pull request introduces the initial implementation of the paragon build-tokens CLI command within the Tutor plugin ecosystem. It leverages a lightweight Docker container and Tutor's custom job framework to facilitate the building of Paragon design tokens.

Key Changes

Docker and Build Process

• Dockerfile (paragon-builder): Added a Dockerfile for the Paragon Builder, which uses a Node.js Alpine base image to install the Paragon CLI and execute theme builds.
• Entrypoint Script (entrypoint.sh): Added a script to handle argument parsing and the theme compilation, it integrates with tutor jobs execution framework.
• Docker Compose Service: Added a paragon-builder-job service in local-docker-compose-jobs-services to run theme builds as Docker-based jobs.

Command Execution

• Custom Tutor Command: Registered a custom do command (build_tokens) in plugin.py to enable the flexible theme building via the Tutor CLI. This command supports options for source-only builds, token references, specific themes, and verbose logging.

Usage Instructions

1. Build the Docker Image:
   After installing and enabling the plugin, build the Docker image with the following command:

   tutor images build paragon-builder

2. Run the Build Job:
   Execute the build job using:

   tutor local do build-tokens <options>

   Note: A comprehensive list of available options for the build-tokens command can be found in the README.rst file.

[Ang-m4]

This PR is already under review right here: openedx#34