Problem
The current Docker section in the README only provides links to the container images but does not include clear instructions on how to use them.

This makes it difficult for new users to quickly run kiwix-serve using Docker.

Proposed Solution
Add step-by-step instructions including:

• docker pull command
• docker run example with port mapping and volume mounting
• example showing how to load a ZIM file
• brief notes for common pitfalls

Why this is useful
This will improve onboarding for new contributors and users by making it easier to run Kiwix tools without building from source.

Additional context

This improvement focuses on documentation clarity and usability.