Update docs and contributing files to facilitate access to OEO for new users

[chrwm]

Description of the issue

So far only instructions for implementations--> wiki/how to implement

• [ ] Revise CONTRIBUTING and explain requirements (Academy course, meetings, interaction with issues) and refer to wiki, but details elsewhere
• [ ] Read and sort wiki, Academy course and contributing again
  • [x] wiki
  • [ ] academy course
  • [ ] contributing
• [ ] Readme as an introduction, work out the collaboration section and refer to the rest https://contributing.md/how-to-build-contributing-md/

Workflow checklist

• [ ] I am aware of the workflow for this repository