Adjust auto-publishing workflow

[aSemy]

Adjust the 'publish' workflow so that it's called by the 'build' workflow as a reusable workflow

This hopefully fixes the issue described in #106

@aSemy : any idea why "Publish" workflow gets triggered for PRs? I thought the if condition in the job should prevent that? Obviously, I am wrong :D

Originally posted by @Quillraven in #106 (comment)

I'm not 100% certain that this will solve the issue, so please double check it!

[aSemy]

Seems to work as expected for pull requests, so the publish workflow is skipped

Hopefully the publish workflow will be triggered correctly when 'build' runs on the master branch!

[aSemy]

I see that the 'publish' workflow is still triggered: https://github.com/Quillraven/Fleks/actions/runs/5574312973/workflow

This is because GitHub is still picking up the unmodified publish.workflow that's on the master branch. The at 1336150 links to the master branch version: 1336150

I expect that the publish workflow will no longer be triggered when the 'build' workflow completes if this PR is merged is merged in.

[Quillraven]

Let's merge it after the small change (if you agree) and then test it ;)

Thank you for your quick look into this issue.