Better English in the README.

To see the actual changes better, run locally

```bash
git diff --color-words=[A-Za-z] master..better_readme
```

@jreidinger Thank you for the README! To proofread it, I had to read it ;-) and it is good!
A working one is https://github.com/yast/yast.github.io/blob/master/doc/architecture.md but the one preferred is probably https://yastgithubio.readthedocs.org/en/latest/architecture/