Not sure about the yml files. I recognize the github files, but not the yml files. Do they also have to do with versioning maybe? I also suspect these are library files you included for other developers? So maybe you could relay this to them?
The vendor folder contains 3rd party libraries. It is included as is. The .github and other files you mention are simply part of those libraries as they are imported.
There is no harm at all having these files be included.