Add prompt before tagging Gutenberg

[jhnstn]

While in most cases tagging after creating the PR should be safe there are cases where a minor change needs to be added after the release script has ran. This is usually just a change note update.

We should add a prompt before tagging to

1. Allow the wrangler to review the PR on Github before the tag is created
2. Allow the wrangler to skip the tagging

In the later case we might want to print out the git tag command since our manual instructions have resulted in a mix of lightweight and annotated tags on Gutenberg. This should be output at the very end of the command run especially during a prepare all run since the tagging step is in the middle of the run.