Improve documentation

[nwneisen]

The project could use some improved documentation. This is a ticket to track initial topics that come to mind. These should be setup to follow gihub's expected MD locations.

• [ ] Design overview & history
• [x] How to install an use cri-dockerd
  • [ ] Give examples for major environments using the project
• [x] A development setup
• [x] How to build the project from source
• [x] How to run the built binary in a development environment (minikube or something similar)
• [x] How to run the tests
• [ ] Contributing guidelines
• [x] Code of Conduct
• [ ] A release process and cadence
• [x] Contributors file

[2rs2ts]

This just came up in the slack channel as a potential docs improvement; if you want to add it in your checklist please feel free:

• [ ] Elaborate on what the options for --network-plugin are and why a user would need to set it to anything instead of leaving it at the default