Feature request: Close draft PRs only

[BillyONeal]

Description: We use "draft" status as "contributor is working on this" and mark PRs draft again after reviewing and there are things that need edited. We only want to run the stale bot on draft PRs that have had no activity for 6 months. Unfortunately, there's only an exclude-if-draft option, not an include-if-draft-option.

Justification: (see above)

Are you willing to submit a PR? Possibly? I'm not super familiar with how to make such contributions though. I believe it should be fairly similar to https://github.com/actions/stale/blob/3f3b0175e8c66fb49b9a6d5a0cd1f8436d4c3ab6/src/classes/exempt-draft-pull-request.ts -- just invert the test.