It is not possible to upload an automator workflow 'application', which is just a script, to the store.
"which is just a script"
Um, no. Automator can save a workflow as a standalone application just fine. What it can’t do is save it as a *sandboxed* application, due to technical limitations in the existing AMWorkflow architecture (recently discussed on other threads for those that care about such things). So OP is SOOL as far as distributing Automator-based apps via AppStore goes, though can still distribute it via a personal/third-party website, of course.
With any luck Shortcuts will appear in macOS 10.15 as a modern, safe, sandbox-compatible successor at which point this is all moot anyway, although it sounds like there are security weaknesses that have yet to be addressed in that [twitter.com/twolivesleft/status/1088080307457159169] so best not hold breath for immediate AppStore-based distribution either.