Consider add some docs and images about the overall architecture

It would be great to see how does this project work and how overall architecture is designed! Maybe adding some arch.md or some diagrams in the [./docs](https://github.com/containers/netavark/tree/main/docs) folder would be nice to have. 🙏

Start by reviewing the existing material in the ./docs folder and the project structure to understand what architecture is already documented. Define an architecture overview in an arch.md file or diagrams, then confirm that the major components and their relationships are explained clearly for a new reader.

Written by the indexing model from the issue text.