Along with CONTRIBUTING.md, I've been including a WRITING.md in my projects, too. Is it bulletproof? No. But it does help things like READMEs, PR descriptions, and other documentation to be much more readable than your garden variety slop. Enough so that further editing is usually pretty painless.
Would you mind sharing a link? It’s ok if you don’t want to. This is just something I feel like I’ve been really struggling with and would love to see how others are trying to tackle it.