message: docs(readme): update branch description
diff: @@ -20,8 +20,8 @@ Reactive Extensions Library for JavaScript. This is a rewrite of [Reactive-Exten
  ## Versions In This Repository
  -- [master](https://github.com/ReactiveX/rxjs/commits/master) - commits that will be included in the next _minor_ or _patch_ release
  -- [next](https://github.com/ReactiveX/rxjs/commits/next) - commits that will be included in the next _major_ release (breaking changes)
  +- [master](https://github.com/ReactiveX/rxjs/commits/master) - commits that will be included in the next _major_ release (breaking changes)
  +- [next](https://github.com/ReactiveX/rxjs/commits/stable) - commits that will be included in the next _minor_ or _patch_ release
  Most PRs should be made to **master**, unless you know it is a breaking change.
  