The release history is normally where I follow changes of projects. To slap it onto the Readme ... an ever growing list of changes ... isn't how any project does it, so it's not really expected. If in one document, make a breakingChanges.md and link it in the Readme. The nice thing of a release history would be that one could easily find a summary not only of breaking changes but also new "features" and contributors could be mentioned etc. It would definitely something I would love to read as I can't follow all repo activity since a long time now. 

 I don't like putting it on the README either. I think such a document is likely to become outdated and useless regardless of where we put it. 

 Well anywhere we put it can become outdated if not maintained