Mark prelease when in in tag

Author: Garulf

.github/workflows/release.yml

@@ -36,6 +36,7 @@ jobs:
         uses: softprops/action-gh-release@v1
         with:
           draft: false
+          prerelease: ${{ contains(steps.version.outputs.version, '-')}}
           files: "./${{steps.zipname.outputs.zipname}}"
           tag_name: "v${{steps.version.outputs.version}}"
           generate_release_notes: true