Document the current implementation

[NicoVogel]

We should try to create a small documentation which roughly reflects the implementation. As we will not work constantly on this project, it will help us (and others) to quickly come back into the topic.

What should be documented:

• overview of the general process
• a little more detail on the creation of changes (e.g. update file and replace file)

[NicoVogel]

The documentation should be within github wiki, but its currently not possible to create pull requests for the wiki repo. Therefore, I suggest using this action instead: https://github.com/marketplace/actions/publish-to-github-wiki