artifacts-tool: Don't try to create an existing release

[max-privatevoid]

Motivation

What I'm trying to do in https://github.com/hyprspace/hyprspace is:

• Have a package definition in which the version of the overall project is defined. The Git tags should match these versions.
• When I change the version in that package definition (on the master branch), I want to automatically get a new tag (and release) for that version.

To achieve that, I want to use the github-releases effect. By makig it run on every push to master, I can get the desired effect, but when the tag already exists, it'll show an error in CI, which doesn't look nice. So, just check if the tag exists (there may be a better way to do this), and if so, don't do anything.

Let me know if you think this is a useful idea or not.

Maintainer checklist

• Documentation (function reference docs, setup guide, option reference docs)
• Has tests (VM test, free account, and/or test instructions)
• Is the corresponding module up to date?

[roberth]

If you only run it for the tag, wouldn't that solve the problem?

[max-privatevoid]

Then I'd have to create the tag. This way, the effect creates the tag for me.