Add Docker networking scripts and configuration files

- Created a new package.json for the server with Express dependency.
- Added a comprehensive shell script (contenedores-v.sh) for demonstrating Docker networking concepts, including creating networks, running containers, and inspecting configurations.
- Introduced a homework script (deberes-v.sh) for practicing Docker networking tasks.
- Updated README.md to enhance the explanation of Docker networking, including new demos, improved formatting, and additional content for better understanding.

Author: 0GiS0