This used to be called "I hired QA people to identify gaps in my project", but hey now it has become paying people to follow readme
It’s normal to compensate them for their time.
Normally though you don’t modify it after each participant. But for something very niche like following a README (as opposed to an e-commerce flow targeted to the general population) it might be fine, if less rigorous.
As I already mentioned in another comment, I recommend this post for people who want to go a bit deeper: https://www.nngroup.com/articles/usability-testing-101/