Integrate bump-readme into a new step 6 of the process

[joestringer]

André suggested integrating the bump-readme steps into step 4 of the release process:

#304 (review)

[joestringer]

I guess the tricky part about integrating into step 4 is that we run the release process three times, once for each stable branch, so I'm not sure how we would decide to bump the readme (and avoid either posting three PRs or failing to update all three releases)

[joestringer]

Probably it makes sense to just make this a new step 6 instead so we can run once for the three patch releases?

[aanm]

Probably it makes sense to just make this a new step 6 instead so we can run once for the three patch releases?

Oh, I didn't remember about this. That's a good point. We could open a PR in draft and then always updated it with existing releases. Then would be up to the release manager to open the PR as ready for review.