Allow fotingo to work on issues without closing in review

[shakefu]

Often an issue will span multiple PRs and we want to be able to work on an issue without closing the issue when we fotingo review.

Right now we can enable this by simply deleting the Fixes: line from the generated description.

It would be great to have an optional fotingo work-on command which does the correct issue associations, but doesn't close the issue when fotingo review is run against that branch.