Update publish.yml
Update publish.yml

* Add Open-VSX publishing.
* Attempt to only run publish a single time, and reuse the artifact for the other steps.
jbenden/vscode-c-cpp-flylint,jbenden/vscode-c-cpp-flylint,jbenden/vscode-c-cpp-flylint,jbenden/vscode-c-cpp-flylint