Add content descriptions and resource links for 5 empty topic pages in the Docker roadmap's Linux fundamentals section: - Shell Commands - Shell Scripting - Package Managers - Users / Groups Permissions - Programming Languages Each topic now includes a concise explanation of the concept in the context of Docker, along with curated external resources for further learning. Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>