Git GUI and Text Editor for Non-Programmers?

Let me explain: I have a website (https://github.com/finnito/Science) which is a Hugo website and thus mostly Markdown. I use this website to create all my secondary school Science teaching resources.

I am considering trying to find a co-worker or two to work on it with me as to flesh it out and get better material, but here is the catch: Science teachers aren't programmers and don't want to spend time learning the CLI, the intricacies of git or anything; they generally just want to update a file and at most leave a little commit message.

I have spent quite a while making sure the deploy pipeline is quite reliable and am fine with people committing to master etc.

I am looking for a way to best get people set up editing files and contributing without much trouble. Do you have any thoughts or recommendations?